PROJECT SQUID SEMI-ANNUAL PROGRESS REPORT

• Document Type: CREST
• Collection: General CIA Records
• Document Number (FOIA) /ESDN (CREST): CIA-RDP81-01043R002200030011-8
• Release Decision: RIPPUB
• Original Classification: K
• Document Page Count: 74
• Document Creation Date: December 23, 2016
• Document Release Date: August 12, 2013
• Sequence Number: 11
• Publication Date: April 1, 1958
• Content Type: REPORT

Aft.
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ATLANTIC RESEARCHCORPPRATION
CALIFORNIA INSTITUTCOP TEC'ANOLDdY
THE CATHOLIC ?UNIVERSITY OF AMERICA
CORNELL AERONAUTICAL LABORATORY, INC..
UNIVERSITY OF DELAWARE
EXPERIMENT, INCORPORATED
. THE JOHNS HOPKINS UNIVERSITY
MASSACHUSETTS :INSTITUTE OF TECHNOLOGY
UNIVERSITY-OF MICHIGAN', .
NORTHWESTERN UNIVERSITY ?
THE PENNSYLVANIA. STATE UNIVERSITY
PRINCETON UNI,VERSITY
PPRDOE,UNIVERSITY '
STANFORD RESEARCH INSTITUTE'
UNITED STATES BUREAU OF:NINES
UNIVERSITY OF-WISCONSIN '
. "-
Project SQUID is a cooperitive program of bail-c resea?O'relatinsg "to
Jet Propulsion. It is sponsored ,by the Office,of Naval ReseaTsIvand
is administered by'PrincetopYliniversityAh?rough,Ccifitracf Non!. I858(25);
'i
NR-098-038.
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?
I,
STAT
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SEMI-ANNUAL PROGRESS REPORT
PROJECT SQUID
A COOPERATIVE PROGRAM
OF FUNDAMENTAL RESEARCH
AS RELATED TO JET PROPULSION
FOR THE
OFFICE OF NAVAL RESEARCH, DEPARTMENT OF THE NAVY
This report covers the unclassified
work accomplished during the period
October 1, 1957 to March 31, 1958
by prime and subcontractors under
Contract Nonr1858(25), NR-098-038.
JAMES FORRESTAL RESEARCH Uinta
PRINCETON UNIVERSITY
Princeton, N. J.
April 1, 1958
Reproduction in full or in part is permitted for any use of
the United States Government
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Semi-Annual Progress Report
TABLE OF CONTENTS
FLUID MECHANICS
April 1, 1958
Fundamental Investigation of Nonsteady Flow (Cornell) 1
Investigation of Turbulence (Johns Hopkins) 7
Structure of a Detonation Wave (Michigan) 11
Exhaust Nozzle Impedance to High-Frequency Longitudinal Gas
Flow Oscillations (Princeton) 15
TRANSPORT AND TRANSFER PROCESSES
Thermal Conductivity and the Viscosity of Ammonia and
Hydrazine (Cal. Tech ) 19
Thermal Conductivity of Gases and Liquids Over a Range of
Temperatures and Pressures (M.I.T.) 23
Atomization, Vaporization, and Combustion of Multicomponent
Fuel Droplets (Northwestern) 27
Dynamic Conditions in a Spray Zone (Penn State) 33
Statistical Properties of Two-Phase Flow (Princeton) 37
Studies of Heat Transfer to Gases and the Mechanism of Two
Phase Flow (Purdue) 47
CHEMICAL KINETICS
Reactions of Hydrogen Atoms (Catholic Univ.) 65
High Temperature Reactions (Penn State)69
Surface-Catalyzed Atom and Free Radical Reactions (Stanford). . 73
TV. COMBUSTION PHENOMENA
Structure and Burning Mechanism of Laminar Flat Flames
(Atlantic Research) 77
Research on High Pressure Combustion (Bureau of Mines) 81
Investigation of Flame Propagation and Stability with Particular
Reference to the Interaction Between Flame and Flow (Cornell) . 89
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$'71-
ut-al,ts?An
Investigation of the Basic Problems Associated with Gaseous
Combustion (Delaware)
Burning Velocity, Flammability Limits, and Ionization in
Flames (Experiment, Inc.) 105
High Output Combustion (M.I.T.) 113
Ionization in Detonation Waves (M.I.T.) 121
Physical Properties of Various Types of Flames (Princeton). . 125
Theory of Detonations and Flame Propagation in Gases
(Wisconsin)
97
v. INDEX
Index to Reports by Contracting Organizations
VI. APPENDIX A
_
Reports and Publications
VII. DISTRIBUTION LIST
ii
133
135
137
139
?
(.1
,
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Cornell
FUNDAMENTAL INVESTIGATION OF NONSTEADY FLOW
Cornell Aeronautical Laboratory-, Inc. - Phase 1
G. Rudinger, Phase Leader
L. M. Somers
Introduction
Fluid Mechanics
This study is concerned with the extension of theoretical and experi-
mental methods for the analysis of nonsteady-flow problems. Theoretical
investigations of such problems are frequently carried out by means of wave
diagrams based an the method of characteristics, and experimental work is
based on shook tube techniques. Various cases of bound 30447- conditions in
nonsteady flow have been studied. The effect of pressure waves on small
regions where the density differs from that in the surrounding gas is also
being investigated.
1
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Cornell
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Discussion
Fluid Mechanics
Boundary Conditions in Nonsteady Flow. Problems of nonsteady flow in a duct
are usually attacked by means of the method of characteristics. The construc-
tion of the resulting wave diagrams (1) requires a knowledge of the conditions
that govern the reflection of pressure waves from various flow boundaries.
The steady-flow boundary conditions, after being disturbed by an incident pres-
sure wave, require a finite time to readjust themselves to their new steady-
flow level and since this adjustment process is continually modified by
further incident waves, the instantaneous boundary conditions become also a
function of the flow history. The customary technique to avoid this diffi-
culty is to neglect the effects of the finite adjustment time and to apply the
steady-flow boundary conditions. Improved boundary conditions are now sought
that should enable one to determine the errors introduced by the conventional
procedure and that may be used when a high accuracy is required in a wave
diagram.
The investigation of the boundary conditions for open ends was started
with an analysis of the reflection of shock waves (2). The results of this
investigation was later extended to incident waves of arbitrary wave form,
and a paper on this study was published (3).
Another study dealt with the reflection of shock waves from orifice
plates. The technical work on this problem was completed during the previous
reporting period (4). A. paper on this material was presented at a meeting
of the American Physical Society and is also awaiting publication (5).
.1???????.....?????????????????
2
Cornell
Fluid Mechanics
An attempt is being made to extract effective boundary conditions for
shock reflection at a flame front from experimental observations such as
those previously obtained under Phase II of this contract (6). Only some
preliminary work has been done so far on this problem. A. review of the
present knowledge on shock wave and flame front interactions was prepared for
presentation at the Third Colloquium of the AGARD Combustion and Propulsion
Panel. Although this paper was not prepared as part of Project SQUID, it is
based to a large extent on work carried out under this contract and has,
therefore, been given advance distribution under this project (7).
Effect of Pressure Waves on the Motion of Small. Regions of Different Gas
Density. It had previously been reported (4) that small gas "bubbles" the
density of which is different from that of the surrounding gas do not follow
an accelerated motion of the latter, such as that produced by pressure waves.
The described effect can be qualitatively explained by the buoyancy of the
"bubble" in the gravitational field that produces the same acceleration as
the pressure waves. A relation for the ratio of the velocity of the bubble
and that of the surrounding gas was derived which involved the density ratio
as the main parameter. When the data for helium and sulphurhexafluoride
"bubbles" in air were substituted, the results differed from the previously
obtained experimental values by a factor of about 2. The reason for this
discrepancy seems to be that the derived formula strictly applies only to
solid particles. The energy acquired by the particle differs from that re-
quired for it to stay at rest with respect to the surrounding gas. This
energy difference can then only appear as kinetic energy of the relative
3
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Cornell
Fluid Mechanics
motion. In the case of a gas bubble, only part of the energy goes into the
translational motion while the rest is used up in the generation of vorticity.
To obtain agreement with the experimental observation, one would have to
assume that about one-quarter of the energy goes into translation and three-
quarters into vorticity generation. An attempt will be made to find a
theoretical reasoning to derive this energy ratio independently.
A paper on the experimental part of this study was presented at a meet-
ing of the Fluid Dynamics Division of the American Physical Society (8) and
the material will be written up for publication.
Notes and References
1, G. Rudinger, Wave Diagrams for Nonsteady Flow in Ducts.
D. Van Nostrand Company, Inc., Princeton, 1955
2. G. Rudinger, On the Reflection of Shock Waves from an Open End of a Duct.
Journal of Applied Physics, 26, 981-993 (1955)
3. G. Rudinger, The Reflection of Pressure Waves of Finite Amplitude
From an Open End of a Duct. Journal of Fluid Mechanics 3,48-66 (1957)
L. Project SQUID, Semi-Annual Progress Report. 1 October 1957, pp. 1-6
5. G. Rudinger, The Reflection of Shock Waves from an Orifice at the End
of a Duct. Paper presented at the New York City meeting of the American
Physical Society, January 29-February 1, 1958. (Submitted to
Zeitschrift fir angewandte Mathematik and Physik for publication)
4
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Cornell
Fluid Mechanics
6. G. Mbrkstein, A Shock Tube Study of Flame Front-Pressure Wave
Interaction. Sixth Symposium (International) on Combustion, Reinhold,
New York, 1957, pp.387-398
7. G. Rudinger, Shock Wave and Flame Interactions. Paper prepared for
presentation at the Third AGARD Combustion and Propulsion Panel
Colloquium, Palermo, Sicily, March 17-21, 1958. (Proceedings of the
meeting to be published) Preliminary issue on microcard as Project SQUID
Report No. CAL-74-P, December 1957, ASTIA AD-147699
8. G. Rudinger, The Effect of Pressure Waves in a Gas on the Motion of Small
Regions of Different Density. Paper presented at the meeting of the
Fluid Dynamics Division of the American Physical Society, Bethlehem, Pa.,
November 1957
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Johns Hopkins Fluid Mechanics
INVESTIGATION OF TURBULENCE
The Johns Hopkins University - Phase I
Leslie S. G. Kovasznay
Introduction
The research program of the Department of Aeronautics reported here
is jointly sponsored by Project SQUID Nonr 1858(25) and by the Navy Bureau
of Ordnance under contract Nord 15872.
During the period several problems were investigated.
Discussion
(a) Transistorized hot-,wire anemometer. The major result obtained
in the report period is the successful development of a.simple rugged
transistorized hot-mire anemometer.
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Johns Hopkins
Fluid Mechanics
The hot-wire anemometer in general is a rather delicate and expensive
complex of instrunents so that the use of more than a few channels appears
to be prohibitive. As soon as transistors of reasonable reliability became
available, it occurred to us that their use for hot-wire anemometers may
radically change this outlook.
The hot-wire anemometer is a low impedance (5 - 50 ohms), low voltage
(.5 - 1.5 volt) device requiring relatively high currents (20 - 100 mA).
Constant temperature operation attained with negative feedback has its
attractions but it is rather involved when high impedance vacuum tubes are
used as active elements. Impedance matching with transformers have their
own difficulties, consequently the constant temperature (feedback) system
in most cases did not compete with the constant current system employing
electronic compensation of thermal lag.
We found that the transistors being low impedance devices are natural-
ly matched to the hot-wires and we succeeded in developing a constant tem-
perature negative feedback hot-wire set that fits into a 2 1/2" x 1 1/2"
x 1" box containing seven transistors, two wire-wound potentiometers and
about eleven fixed carbon resistors. Twelve volt d.c. power is required.
The performance of the instrument is as follows: Using a .0001" Platinum
wire we obtained a frequency response corresponding to a damped RCL reson-
ance circuit with a resonance frequency of 17 kC, the damping can be varied
but critical damping was found to be the most convenient. Square wave rise
time was found, 30 . 37 microseconds. Feedback ratio (suppression of tem-
perature fluctuations) is 200 - 300. Noise level is equivalent to a
8
S.
Johns Hopkins Fluid Mechanics
turbulence level of .01 - .02%. The output of such a system is a signal of
the order of 1 - 3 volts at a very low impedance (about 50 ohms). By the
use of two cascaded squaring circuits it is possible to attain a strictly
linear velocity-voltage-output relationship. We are continuing to work on
a transistorized linearizing circuit that would permit the use of hot-wire
equipment as a linear velocity pick-up. Even before attaining that goal
we have used the two units with commercially available squaring circuits
and attained full linearity by direct calibrations.
(b) Orifice hot-wire pressure probe, During the period covered only
little progress was made because the research worker (graduate student) was
on leave of absence to complete certain academic requirements. The device
has been in a sufficiently advanced stage so experimental work will be re-
sumed about April 1.
(c) Spinning wake. An experiment was attempted to produce an axisym-
metrical wake with a superimposed swirl in a supersonic flow. The chief
interest is the exploration of temperature effects. A cruciform wing model
with a cylindrical central body was fabricated and mounted in the Department
of Aeronautics supersonic wind tunnel. The angle of attack of the four
wings was controlled by hydraulic means. The preliminary tests at a Mach
number 1.75 and atmospheric stagnation conditions have indicated that aero-
elastic flutter occurred and after only a minute run the structure was
permanently strained. The entire approach to the problem might need revi-
sion.
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Johns Hopkins
I 1
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Fluid Mechanics
(d) Laminar to turbulent transition. A new experimental program is
planned to investigate the transition from laminar flow to turbulent flow.
The specially interesting phase is the breaking down of regular periodic
instability waves into "turbulent spots". Preliminary reports from other
laboratories (principally, National Bureau of Standards) indicate that these
are essentially three-dimensional phenomena. Our new approach involves the
use of a larger number of hot-wire probes (up to 15 - 20) that was pre-
viously prohibitive but became possible with the development of the new
simple transistorized hot-wire channels. A simultaneous record of the
velocity (on a linear scale!) give us a strong hope to reconstruct the model
of turbulent spot generation.
(e) Publications during the period. Reporting results obtained
under present contract. ?
(1) Betchov, R.: On the Fine Structure of Turbulent Flows, Journal
of Fluid Mechanics, Vol. 3, Part 2, p. 205, Nov. 1957.
(2) Kovasznay, Leslie S. G. & Arman, All: Optical Autocorrelation
(3)
of Two-Dimensional Random Patterns, Rev, Sci. Instr., Vol. 28,
No. 10, p. 7934 October 1957.
Chu, B. T. & Kovasznay, Leslie S. G.: Nonlinear Interaction in
a Viscous Heat-Conducting Compressible Gas, Jour. of Fluid
Mechanics, Vol. 3, Part 5, p. 494, February 1958.
10
A
Michigan Fluid Mechanics
STRICTURE OF A DETONATION WAVE
University of Michigan - Phase II
T. C.. Adamson - Phase Leader
R. Gealer, R. Ong, D. Wilcox
Introduction
This phase of Project Squid is divided into three tasks.
a) Structure of a Detonation Wave
b) Gaseous Detonations at High Pressure
c) Interaction of Discontinuities
The first subject is a theoretical investigation, while the last two
cover both theoretical and experimental work.
Discussion
The purpose of this investigation is to use techniques evolved in the
study of deflagration waves in the study of detonation waves in an attempt to
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Michigan
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Fluid Mechanics
relate the dynamic parameters to the chemical parameters. The wave is assum-
ed to be a shock followed by combustion and attention is focused on the com-
bustion process.
The simple system described in the previous progress report (April, 1957)
is still being considered. The temperature and velocity have been expanded
around their values at the hot boundary, in terns of the concentration of the
combustible. Second order expansions must be used since the temperature, for
example, goes through a maximum if the firml Mach number is greater than a
critical Mach number, defined in terns of the ratio of specific heats, the
molecular weight change, and the heat added. The expansions indicate that a
singularity exists in the limiting Chapman-Jouguet case, so that the results
would be inconclusive in this case. For this reason, expansions of the neces-
sary variables around the point of maximum temperature rather than the point
of final temperature, are being considered. These functions can be found,
but they add considerable complexity to the integral involved in the final
solution. Hence, a careful order of magnitude analysis of the terns in the
integrand is being made so that unnecessary terns may be eliminated. A mem-
orandum covering the work done has been written and will be available soon.
Gaseous Detonations at High Pressure
This phase has been finished, and a report has been written. This work
Is being submitted as a thesis for the Ph. D. by 1&". Gealer, and will be
available in report form after its publication as a thesis. The results show
good agreement between calculated and measured detonation wave velocities in
hydrogen-oxygen mixtures in a range of initial pressures from 14.4 Psi to
1000 Psi, and initial hydrogen concentrations of 40% to 80% by volume. Cal-
Michigan Fluid Mechanics
z
culated wave velocities were found by assuming chemical equilibrium to exist
behind the wave. Since gas properties at the higher pressures were not known
accurately, an analysis of possible errors in wave velocity due to given
errors in these properties was made. This analysis indicated that to first
order, no appreciable errors were introduced by the assumed properties.
Interaction of Discontinuities
This phase has been completed and a report is being written. The exper-
imental work on a shock - contact discontinuity interaction has been completed
and shows fair agreement with, theoretically predicted results.
1
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Prinoeton
EXHAUST NOZZLE IMPEDANCE TO HIGH-FREQUENCY
LONGITUDINAL GAS FLOW OSCILLATIONS
Princeton University - Phase 9
L. Crocco, Phase Leader
J. Grey, R. Monti
Introduction
Fluid Mechanics
This investigation was initiated in order to study the effects of
sustained longitudinal oscillations on the boundary condition represented
?
by the exhaust nozzle of a combustion chamber. The primary purpose of
the study was to correlate existing theories (I, 2, 3) with experimental
measurements of the important nozzle flow parameters in the absence of
combustion. The significant parameter which beat describes the nozzle
boundary condition has been called the nozzle admittance (reciprocal
impedance), defined in (2) as the ratio of instantaneous fractional
oscillations of gas velocity and density at the nozzle entrance.
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I
um:
Princeton
Fluid Mechanics
As described in the previous report, non-availability of satisfactory
hot-wire equipment for instantaneous velocity measurements necessitated an
Indirect evaluation procedure. The results of these indirect experiments
were highly satisfactory, indicating excellent correlation with theoretical
predictions on a number of different nozzles for all system variables
tested. The only significant departure from theory was caused by viscous
and inertial damping, not considered in the analytical treatment, which
produced experimental amplitudes several times smaller than predicted.
Discussion
Having completed an indirect evaluation of the analytical method,
efforts to provide the direct velocity-density measurement required for
nozzle admittance were continued. Some time was spent in moving the
apparatus to a safer and more advantageous location in a protected test
area, and a commercially available constant-current hot-wire amplifier
and probes were purchased from the Flow Corporation.
Initial testing to determine the required probe configuration with
respect to sensitivity, strength, and frequency response was completed. It
was found on these tests that the turbulence level in the duct was
excessive, and its amplification (proportional to frequency for the constant-
current amplifier) was greater than that of the signal level. Application
of electronic filtering was only partly successful, and consequently a
16
I.
Princeton
Fluid Mechanics
combination of turbulence-elimination techniques, including duct polishing,
turbulence screens, bell-mouthed inlets, and stagnation-tank packing are
now being evaluated.
Data on several linear nozzles with different entrance Mach numbers,
admittance ratios, and area ratios, as well as at least one conical nozzle
and several orifice configurations, will be collected upon achievement of
satisfactory turbulence-level characteristics. The effect of viscous
damping is also being introduced into the theoretical analysis in order
to provide better correlation with the experimental results.
References
I. Tsien, H. S., "The Transfer FunCtIons of Rocket Nozzles," Journal
the American Rocket Society 22, 1952, p. 139.
2. Crocco, L., "Supercritical Gaseous Discharge with High Frequency
Oscillations," Aerotecnica 33 1953, p. 46.
3. Crocco, L., and Cheng, S. I., "Theory of Combustion Instability in
Liquid Propellant Rocket Motors," AGARDograph No. 8, Butterworths
Publications Ltd., London, 1956, Appendix B.
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Cal. Tech.
Transport and Transfer Processes
THERMAL CONDUCTiurf AND THE vIscosin
OF AMMONIA AND HYDRAZINE
California Institute of Technology - Phase 2
B. H. Sage, Phase Leader
Introduction
Experimental measurements of the viscosity of ammonia in the gas and
liquid phases are under way. Measurements have been obtained for the gas
phase at pressures from atmospheric to vapor pressure and at temperatures
between 1000 and 250? F. Work is in progress at the present time to
determine the viscosity of the gas phase at higher temperatures.
The measurements are being made with a rotating-cylinder viscometer made
available to this project by the California Institute of Technology.
As a preliminary study, the viscosity of n-pentane in the liquid phase
was determined at pressures up to 5000 pounds per square inch and at
temperatures between 1000 and 3400 F. No difficulty was experienced in
carrying out these investigations and evaluation of the results indicates
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F
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Cal. Tech. Transport and Transfer Processes
that the data are in good agreement with earlier measurements upon the
viscosity of n-pentane.
Revision of the thermal conductivity equipment, in order to eliminate
direct contact of the thermocouples with the fluid under investigation, is
under Way, and it is expected that the revised equipment will be in operation
by May 1958.
A manuscript describing results obtained during Phase 1 of this program
upon the thermal conductivity of nitrogen dioxide has been published (1).
A second manuscript describing the thermal conductivity of nitric oxide has
been submitted to the editor of Industrial and Engineering Chemistry as a
contribution to the Data Series of that journal. From the favorable comments
of the reviewers, it is expected that the paper will be accepted. A third
manuscript which describes the results obtained upon the thermal conductivity
of nitrous oxide has been prepared and is being transmitted to Project SQUID
for publication as a report of a portion of the activities of this project in
the field of thermal conductivity.
Discussion
In connection with the evaluation of the thermal conductivity of the
oxides of nitrogen, difficulty has been experienced for several years from
the use of thermocouples in direct contact with the fluid undergoing
measurement. For this reason, it was decided to revise the equipment, and
plane were made to accomplish the revision in the early fall of 1957.
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Cal. Tech.
Transport and Transfer Processes
However, during the move of the Chemical Engineering Laboratory to permanent
quarters in the Eudora H. Spalding Engineering Laboratory, a large lathe
provided with special attachments for the machining of spherical parts was
severely damaged, and a delay of approximately three months in the revision
of the thermal conductivity equipment resulted. Therefore primary emphasis
during the past semiannual period has been upon viscosity measurements.
The rotating-cylinder viscometer has been found to be a very
satisfactory instrument for the determination of the viscosity of fluids at
elevated pressures. From the dimensions of the instrument and the elastic
properties of the suspension for the stator, it was possible to determine
upon an absolute basis the viscosity of air and of n-pentane with a maximum
deviation from established values of 0.4 per cent. Since the total clearance
between the rotor and stator is approximately 0.020 inches, this deviation
involved an absolute uncertainty in the clearance of less than 0.0001 inch.
The rotating-cylinder viscometer is a much more satisfactory instrument than
the rolling-ball viscometer which has been employed heretofore in this
laboratory for measurement of the viscosity of gases and liquids.
A supply of hydrazine has been obtained so that studies of the viscosity
of hydrazine can be undertaken as soon as the work upon ammonia is completed.
It is probable that the maximum temperature at which hydrazine can be
investigated will be limited by the thermal rearrangement of this compound
at elevated temperatures. In the early stages of the program, it may be
necessary to limit the maximum temperature to 160? F. in order to avoid
21.
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- n .
Cal. Tech.
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Transport and Transfer Processes M.I.T.
u
significant probabilities of serious damage to the equipment which could
result from the rapid thermal rearrangement of the hydrazine.
Notes and References
1. G. N. Richter and B. H. Sage, Chemical & Engineering Data Series, 2,
61,66 (1957).
22
Transport and Transfer Processes
THERMAL CONDUCTIVITY OF GASES AND LIQUIDS
OVER A RANGE OF TEMPERATURES AND PRESSURES
Massachusetts Institute of Technology - Phase 2
Frederick G. Keyes, Phase Leader
? Introduction
The low temperature equipment is still not completely assembled.
However, the new jigs were completed and are an important aid in the
difficult cell assembly. The -10 to li.O0?C installation has been developed
to where it is efficient and dependable in use, and the accuracy attainable
is two tenths of one percent. The completion of the carbon-dioxide measure-
ments clears the way to a program of measurements on a variety of sub-
stances. The new high temperature cell is not yet in operation.
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M.I.T.
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Discussion
Transport and Transfer Processes
The functioning of the intermediate temperature cell installation
(-10? to 400?C) continues to be highly satisfactory and investigation of
the thermal conduction behavior of carbon dioxide in the critical region:
31.04?C plus and minus 30?, a density range from essentially zero to the
critical density, 0.474 to 0.93 gicm3, greatest pressure 195 atms., is
completed.
In the course of the carbon dioxide investigation many interesting
observations were made of conditions under which turbulence can be induced:
1. As the critical point was approached, turbulent convection in
the cell was encountered for very low temperature rises, and thus the
temperature rise permissible was very limited.
2. When measurements were made at high enough pressures to liquefy
the CO2 in the lead lines at room temperature, and the cell was above room
temperature, turbulence around the electrical leads caused excessive
fluctuation of the thermocouple voltages.
Additional equipment has been developed to overcome the second phenomenon,
and exceptional accuracy in thermocouple thermometry has been achieved.
Without the new automatic pressure regulation and measurement,
reliable results would have been all but impossible of attainment. The
extremely high compressibility of a fluid in the critical region necessitates
exceptional control of the pressure) to be able to specify the density with
reliability. Valid measurements cannot be made with any large fluctuation
of pressure.
?
24
?????????
tr.
(7774
Declassified in Part - Sanitized Copy Approved for Release 20
M. I. T.
Transport and Transfer Processes
These extensive improvements in equipment have permitted conduction
measurements within 1?C of the critical temperature at the critical
pressure and this is the nearest approach to the critical point that has
ever been achieved. Measurements at exactly critical temperature appear
to be impossible because the fluid is unstable.
The complete interpretation of the thermal conductivity measurements
dbtained for carbon dioxide by others is greatly obstructed through the
lack of pressure-volume-temperature data in the critical region. There is
a possibility that an interested member of the physical chemistry staff
may undertake to carry out the required detailed p-v-T measurements on
carbon dioxide in the critical region. It may be worth remarking that
detailed p-v-T data do not exist for any substance sufficient for interpret-
ing critical region thermal conductivity data taken at random. The
temperatures selected for the present research correspond to the isotherms
of Michels and Michels, or of Michels, Blaisse and Michels, and thereby the
uncertainty as to density is greatly reduced.
The correlation attempts employed for the data for carbon dioxide
indicate unmistakably that the effect of pressure increase or the excess
conductivity over the "zero" pressure value, is a function of density only
or the density quotient with Kelvin temperature. This fact is also of
considerable importance for extrapolation purposes. Papers are in
preparation giving full information on the cell design, its theory and
calibration, along with a full account of the new carbon dioxide data
including the correlations.
25
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, si.41
M. I . T.
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Transport and Transfer Processes
The following series of substances will now be investigated using
the intermediate temperature equipment: argon, helium, nitrogen, mixtures
of nitrogen and helium, hydrogen, carton monoxide, methane and ammonia.
All these gases will be measured for thermal conductivity over a range
of pressure and from -100 to 400?C.
26
Northwestern
Transport and Transfer Processes
ATOMIZATION, VAPORIZATION, AND COMBUSTION OF MULTICOMPONENT
FUEL DROPLETS
Northwestern Technological Institute - Phase 1
W. F. Stevens, Phase Leader
S. Bernsen, J. S. Chinn, M. Engel, G. G. Lamb, and P. A. Nelson
Introduction
This study concerns the atomization, vaporization, and combustion of
multicomponent fuel sprays under conditions approaching those existing in
the combustor of a turbo-jet engine. In particular, an understanding of the
mechanism of pre-flame atomization and vaporization of sprays from pressure
nozzles is being sought, with the hope that this knowledge will enable future
prediction of the combustion behavior of such a spray.
Discussion
Extensive experimentation has been carried out to determine drop-size
1
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27
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Northwestern Transport and Transfer Prooesses
distributions resulting from a wide variety of spraying conditions with a
substantial number of different liquids. The modified liquid nitrogen tech-
nique, as described in previous progress reports, has been employed, and the
data obtained have been successfully correlated. At present, a paper is being
prepared for publication, reporting the results in detail.
The nozzles used in this work were Spraying Systems Co., Type SL, a
grooved-core type with interchangeable orifice inserts and core-pieces. Care-
ful choice of components used resulted in a wide variation of nozzle parameters.
The orifice diameter ranged from 0.0135 to 0.081 inches and the cone angle
varied from 52? to 91?, resulting in capacities ranging from 4.0 to 112 gal/
hour, when spraying water at 1000 psi. Seven different liquids were sprayed,
chosen on the basis of their physical properties, as follows: cyclohexane,
carbon tetrachloride, n-octyl alcohol, nitrobenzene, water, aniline, and
1,11202 -tetrabromoethane. The densities of these materials range from 0.774
to 2.95 gm/cc, their viscosities range from 0.879 to 8.29 cp., and their
surface tensions range from 24.5 to 72.0 dynes/cm. These ranges include
practically all fuels presently being sprayed with pressure nozzles.
For all of the materials and nozzle combinations investigated, the data
appear to fit the square-root normal distribution. This was determined by
plotting the cumulative mass versus the square-root of the sieve size on
normal probability paper. In all cases, a straight line was obtained. The
square-root normal standard deviation was determined from the resulting
straight line, by subtracting the square-root normal mean from the drop-size
28
3
Northwestern
Transport and Transfer Processes
at one standard deviation above the mean, corresponding to 84.13 masstpercent.
By trial and error plotting of the data, it has been found that the mean
drop diameters obtained from runs involving the six organic liquids with
nineteen different nozzle orifice and core insert combinations, over a
pressure range from 100 to 1500 psi, could be correlated according to the
following relation:
Y = 0.0811 Z2 + 0.124 Z - 0.186
5k
where Y = log10 /D
(it 1.2
f-Reke0.55
Z = logio I.
1
, Va
(refer to nomenclature at end of report)
The average deviation of the experimental mean diameters from this curve was
8.25%.
The mean drop-size data for water do not agree with that for the organic
liquids, being from thirty to fifty percent larger than predicte4 by the
relation given above. The reason for this deviation is not known, although
it is probably related to the fact that water does not wet the nozzle well.
However, the data for water appear to be reliable, since they agree well
with available data of other investigators. By trial and error plotting, as
before, the data for water obtained in thie investigation (plus that of others)
have been correlated according to an equation much like the one used for the
organic liquids. In this case, the average deviation of the data from the
29
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Northwestern
curve of best fit was only 6.7%.
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Transport and Transfer Processes
The square-root normal standard deviation data have also been success-
fully correlated, to give a similar curve of best fit. The average deviation
of the data from this curve is 13.0%. The greater scatter of the standard
deviation data is to be expected, since this parameter can be greatly affected
by slight inaccuracies in the sampling or measuring technique. The fact that
the standard deviation could be correlated as well as it was for such widely
different liquid properties and nozzle parameters is indeed gratifying. It
substantiates not only the method of drop-size measurement, but also the
choice of variables for the correlation.
The correlations developed as a result of the research described above
should make it possible for the combustion engineer to predict accurately
the drop-size distribution which will result when a particular fuel is spray-
ed from a nozzle of given properties. Conversely, he should be able to speci -
fy the nozzle dimensions required to give a desired drop-size. Future work
will attempt to determine the generality of the correlations, by operating
other types of nozzles and determining whether the drop-size distributions
resulting are consistent with the data already obtained.
Nomenclature
Do - nozzle orifice diameter, microns
Re - Reynolds No. (dimensionless)
30
Northwestern
Va
Vt
We
)(
Transport and Transfer Processes
- axial fluid velocity, cm/sec.
- tangential fluid velocity, am/sec.
- Weber No. (dimensionless)
- mean drop diameter, microns
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31
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Penn State
Transport and Transfer Processes
DYNAMIC CONDITIONS IN A SPRAY ZONE
The Pennsylvania State University, Phase No. 2
William E. Rans
Hikmet Binark
Introduction
As a basis for understanding the detailed processes of heat and mass
transfer in the combustion of a fuel spray, this research concerns a study of
the dynamic conditions in a spray sone and the reasons why these conditions
exist. Quantities to bestudied include dispersion of liquid flux around a
geometrically fixed plane or center line of flaw, liquid velocities, spray
liquid densities, and air path-lines and air velocities throughput the spray
region beyond the nozzle orifice. An understanding of the nature of the .
C'
momentum transfer process between primary liquid flow and induced air flaw
and the nature of the air-liquid mixing process is also an objective of the
project.
7aCIAT: a;TOn
ra..7ear,
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t--
\1
Penn State
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Discussion
Transport and Transfer Processes
In the penetration zone of a hollow cone spray, air is induced to
enter the spray sheet at right angles to the sheet, pass through the spray
while changing direction, and take a final direction parallel to the nozzle
axis. The magnitude of the air flow velocity is greatest at the zone of
breakup and decreases as the distance from the nozzle orifice increases.
The air velocity inside the spray is a maximum on the nozzle axis and de-
creases to a value at the inside of the spray sheet which is set by the
velocity at which air is being induced from outside the sheet and by the
spray cone angle. Velocity differences above the minimum value show a
normal type distribution, the result of larger velocities nearer the orifice
and axis. The air flaw is laminar in a scale larger than the size of
individual drops.
Air flow induced through a unit area of the spray sheet at a given
distance from the nozzle orifice can be attributed to a momentum interchange
between the air and drops moving relative to the air at the point in
question. A momentum balance can be considered to hold between 1) the total
drag force on all of the drops passing through a particular area of the
spray sheet at any instance and 2) the component in the spray direction of
air momentum leaving that area.
Drops, at the moment of their formation, are projected through the air
in average directions which generate a spray cone. Because induced air
crosses their paths at nearly right angles, drops travel as part of the
_
54
t% '
Penn State
Transport and Transfer Processes
spray sheet only so far as their penetration distance in still air, after
which they move inside the cone and travel parallel to the nozzle axis
joining the induced air flow. The inward bending of drop trajectories,
caused by the air flaw, is also the cause of decreased spray cone angle at
increased distance from the orifice.
The velocity of air entering the spray at a given distance from the
orifice is directly proportional to the velocity of liquid issuing from the
orifice. The magnitude of this velocity is of the order of one-tenth that of
liquid velocity, for example, an air velocity of one-tenth the liquid issue
velocity was measured at two inches from the orifice of a small oil burner
nozzle. For small fuel nozzles (up to 30 gallons per hour) the magnitude of
this velocity is insensitive to variations in spray cone angle and changes
in capacity resulting from changes in orifice diameter. The velocity of air
at any point outside the spray sheet is set by the velocity of air entering
the sheet and the geometrical requirements of continuity. The velocity of
air inside the spray is equal to the velocity outside the spray divided by
the sine of half the spray cone angle. A negative static gauge pressure is
also detected inside the spray.
Mist and air fluxes inside a hollow cone spray are such that the air -
liquid-ratio is a minimum on the spray-axis and increases in a parabolic
fashion to the spray sheet. In fuel sprays the air and fuel mist moving
along the axis can be a rich mixture. Stoichiometric ratios occur at
distances of the order of one inch from the axis.
35
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Penn State
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Transport and Transfer Processes
In solid cone sprays air is also induced into the spray at right angles
to the spray direction. Inside the spray it turns in the direction of the
nozzle axis which, in this case, is also the direction of the spray. Air
and liquid velocities, fluxes of air and liquid, and momentum flux, in a
spray cross section are distributed in a somewhat normal fashion across the
spray axis. A momentum balance exists between the liquid issuing from the
orifice and the two-phase flow at any cross section along the spray axis.
A series of experiments, which demonstrate these qualitative and
quantitative aspects of the induced air flow in hollow and solid cone sprays,
have been performed.
36
;
Princeton
Transport and Transfer Processes
STATISTICAL PROPERTIES OF TWO-PHASE FLOW
Princeton University, Phase 11
S. L. Soo
A. F. El Kouh
R. L. Peskin
C. L. Tien
A. W. Black
Introduction
Turbulent flow processes involving the suspension of solid particles
in an air stream was studied to further the understanding of turbulent
transport phenomena involving two phases. Devices involving two-phase
flow are solid propellant rockets and combustion dhaMbers for solid and
liquid fuels. In the combustion of liquid droplets, one is interested not
only in high evaporation rate, but also in large particle diffusivity,
since the smallest droplet size does not provide the best distribution.
(1) In the case of a solid propellant rocket, the contribution of speci-
fic heat and mass flow of solid particles is obviously held back by the
turbulent dissipation between phases; studies to date have not accounted
for the latter (21 3).
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37
r.??
Princeton
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Transport and Transfer Processes
Many studies were made on the dynamics of particle motion in a fluid.
The study of oscillatory motion of a solid sphere in a viscous fluid was
made by Stokes (4). The motion of a pendulum in a turbulent fluid was
made by Lin (5). The general equation governing particle motion in a tur-
bulent medium was derived by Tchen (6) and its details were recently re-
considered by Lumley (7,8). Solution of the equation of motion in the
Eulerian system of coordinates was attempted. by Davies (9). In all studies
Stokes law for drag of sphere was assumed, thus limiting the solution to
small particles in a stream of relatively low turbulent intensity.
Based on each premises, study based on statistical distribution was
made as published in Ref. (10), neglecting relative acceleration (4,6)
and. probability of space coordinate and approximating the distribution
of stream turbulence as:
f(n)
2,,rx x ? -x i'..
Nre
the following distribution function of turbulent motion of solid. particles
[1]
was obtained:
?
f (n) 2 .srg x e-21r.2n2iru2 -1- 2n2)(1 1 4u-2 1.3 4u2
22 2.2 -
F F 2 A.
where
and
`?frar?-?-e*,..
wow," c......*r??????-??????.??????---
?2
1.3.5 447172
- 23 77- 6") ]
(2]
is the intensity of turbulence of the stream,
is Taylor's (14), a measure of size of eddy of the
stream,
is the frequency
is equal to 18 pi(dp2pp); based on stream viscosity,
particle diameter, and particle density respectively.
-
38
? ?
_
?????
Princeton
Transport and Transfer Processes
The determination of the distribution function is deemed necessary toward
further understanding of the statistics of momentum transfer and our effort
toward determining other transport characteristics. This lead to the con-
clusion of relative Reynolds number of particles:
d 4077- p
Rer = P
Nrs 18 4-2 2 d P
Re ) (-2).
11 p
where (au)2 u - u is the relative intensity between the particle
Pqr-
(intensity 41.12- and the stream (intensity siu ),
We is the Root-mean-squared Reynolds number, ,
and 11 is the Lagrangian scale of turbulence of
Ref. (8) presents this relation as
? aT2r / / ?
Rer = brz-9 L 2 /P) + 1] Re2X
Where
and3 =,./T2 T ? TL being the Lagrangian microscale for time.
L'
Eq. [3] and (4] are identical,for small particles (x3-'1.); the correction
for the apparent mass (4) is a direct one, applicable to the ease Where
p and p are close to each other.
?
Re =
X 1.1.
(c-lx2)3 (L)
X3
the stream.
[3]
Further sharpening of the results from Eq. [2] calls for a more
accurate determination of the distribution function from statistical me-
chanics of this typo of system. This is part of our current effort.
Removal of the restrictions of small particles and moderate turbu-
lence lead to experimental determination of stream and particle motion
(11, 12) in our present phase. Some of the results will be discussed in
the next part.
59
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Princeton
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Transport and Transfer Processes
In this study, we are also concerned with the interaction between the
particles which is significant in the case where solid to fluid weight
ratio is high (13). To understand the phenomena associated with the wall
effect, interaction of particle motion with the wall and non-isotropic
turbulence has been formulated and analyzed through extending the concept
of local isotropy (15).
Discussion
Experimental work to date has yielded data on the turbulence charac-
teristics of both the stream and the particles in the middle third of a
3" x 3" duct. Within this range, the stream is nearly isotropic. For the
range of weight ratio of particles (spherical glass beads) to fluid (air),
no significant interaction between the solid particles and stream has
been observed. This assumption was made in our analytical work on the
particle interaction and wall effect.
The stream measurements so far made with helium tracer diffusion
technique compare favorably with results obtained by other methods (Table
1) (16). The tracer diffusion technique enables us to determine intensi-
ty, diffusivity and scale of turbulence [Row (1) to (8) of Table 21. The
basic technique is presented in Ref. 11 and 12.
The particle motion evaluated from photographic record obtained by
high frequency (6000 to 8000 cycles) successive exposure gives directly
the mean intensity of the particles and the particle diffusivity. Some
of the results so far obtained are presented in Row (9) to (16) of Table 2.
40
Declassified in Part - Sanitized Cov A
pproveci for Release
Princeton
Transport and Transfer Processes
It is interesting to note that for particles giving iTe much greater than 1,
the particle diffusivity (17) is less than stream diffusivity as contrary
to the analytical result. This may be attributed to significant deviation
from Stokes Law in the cases experimented. Further, the intensity of par-
ticles as measured in some cases of low duct Reynolds number, is greater
than that of the stream. This is attributed to increased significance
of wall interaction at low stream velocities. In the case of low mean
velocity of the stream, contribution of exchange of particles between the
middle third and the turbulent field (greater intensity than in the middle)
near the wall is more significant than in the case of high stream velocity
(Row 14, Table 2). The gravity effect for low mean stream velocity case
is also expected to be more significant (Row 15).
The method suggested by Ref. (8) for calculating particle motion
was found to be rather difficult and expensive to carry out. For the
case of particles under isotropic turbulence, with or without the effect
of particle interaction due to Bernoulli force (18), we are working
toward improving the distribution function as approximated by Eq. [2] by
solving the Holtzman equation to obtain its higher order perturbations
(19).
The wall effect on single particle was formulated by considering the
drag force, fluid resistance due to relative particle acceleration, the
fluid inertia, force due to wall turbulence and the buoyancy force.
Effort is made toward solving this integral-differential equation.
4: CIA-RDP81-01043Rnn99nnnqnni 1_52
41
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Princeton Transport and Transfer Processes
References
1. J. P. Longwell, "Combustion of Liquid Fuels" pp. 410 to 417, Vol. II
High Speed Aerodynamics and Jet Propulsion, Princeton University Press
1956.
2. M. Gilbert, L. Davis, and D. Altman "Velocity Lag of Particles in
Linearly Accelerated Combustion Gas" Progress Report No. 20-194.
ORDCIT Project, V.P.L., California Institute of Technology, May 28,
1953.
3. I. Glassman, 'Impulse Expressions for Rocket Systems Containing a
Solid Phase" Jet Propulsions, May 1957, p. 542.
14. A. B. Basset, "A Treatise on Hydrodynamics" 1888, George Bell and
Sons.
5. c. C. Lin, "On the Motion of a Pendulum in a Turbulent Fluid",
Quarterly of Applied Math., 1943, p. 43.
6. c. M. Tchen, "Mean value and correlation problems connected with the
motion of small particles suspended in a turbulent fluid", 1947,
The Hague, M. Nijkoff.
7. S.Corrsin and J. Lumley, "On the Equation of Motion for a Particle
in Turbulent Fluid", Appl. Sci. Res. Sec. A, Vol 6, 1956, pp .114-116.
8. J. L. Lumley, "Some Problems Connected with the Motion of Small
Particles in Turbulent Fluid", Rept., Contract NONR 248 (gi), The
Johns Hopkins University, June 1957.
9. R. W. Davies, "Burtfulent Diffusion and Erosion" J. of Appl. Phys.
V. 23, n. 9, Sept. 1952, pp. 941-8.
10. S. L. Soo "Statistical Properties of Momentum Transfer in Two-phase
Flow", J. Chan. Eng. Sci4 V. 5, pp. 57-67, 1956.
11. H. K. Ihrig, Jr., "The development and design of apparatus and in-
strumentation for the study of the statistical properties of momen-
tum transfer in two-phase flow", M.S.'. thesis, Princeton, 1956.
12. G. H. Paff,"Measurements of Statistical Properties of Two-Phase Flow"
42
Princeton
Transport and Transfer Processes
M.S.E. Thesis, Princeton, Jan. 1958.
13. H. E. Rose and H. E. Barnacle, laaw of Suspensions of Non-Cohesive
Spherical Particles in Pipes", The Engineer, June 14, 21, 1957, PP.
898-906, 939-941.
14. G. I. Taylor, "Statistical Theory of Turbulence", Proc. Roy. Soc.
(London) V. 151, 1935, p. 421.
15. G. K. Batchelor, "Kolmogoroff's Theory of Locally Isotropic Turbulence"
Proc. Camb. Phil. Soc. Vol. 43, p. 533, 1549.
16. H. C. H. Townend, "Statistical Measurements of Turbulence in the Flow
of Air through a pipe" Proc. of Roy. Soc. (London) V. 145, p. 180,
1934.
17. J. Crank, "Mathematics of Diffusion" Oxford Press, p. 10.
18. H. Lamb, "Hydrodynamics" 3rd Edition, Cambridge, 1906, p. 124.
19. S. Chapman and T. G. Cowling "The Mathematical Theory of Non-uniform
bases", Cambridge University Press, Cambridge, 1952.
Table I
Intensity of Turbulence
Reynolds number of duct
Intensity/Mean velocity
Source
12000
.031
.034
.040
Ref. 16
38000
.028
.030
.035
Ref. 16
38000
.0275
Ref. 12
83500
.0224
Ref. 12
129000
.0196
Ref. 12
43
ara.41.+Www,ff ???????,....rneftafil. ; .
_
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17-,0
Princeton
Table 2
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Transport and Transfer Processes
Statistical properties of particle and stream motion
Itam Case
1 Mean velocity
of air, U, fps
2 Reynolds no. of
duct flow
3 Particle flow
rate, lb./min.
4 Particle size,
micron
5 Stream intensity,
4rie, gps.
6 4TeN
7 Scale of turbulence
of streamIllIft.
8 Eddyodigfusivity,
Elfelsec.
9 Particle 4i12
intensity 4L42P
10 Particle diffusivi-
ty, I ,ft2/sec.
11 Scale of turbulence
of particles, ft.
12 Reynolds number
of particles
13 K (Ref. 10)
14 (112z2 )11?
pi/
15 g#1 fps
(ref. 14
16 E /E
1 2 3 4
25 25 25 25
37940 37940 37940 37940
0 .403
250
.270 .394
250 110
.690 .692
.549
.690
.0276 .0277
.0220
.0276
.0562 .0299
.0423
.0435
.0399 .0207
.0232
.0300
2.45
1.84
3.06
1.53
1.53
1.22
*at two stations 2.076 in./1.038 in.
.003/.0017*
.002
.0028/.0017
.00l6
.0011/.0007
.0007
3.58
2.75
.53
321
101
5.65
-3.9
-6.76
-2.1
161
161
103.5
.1
.1
.026
44
Declassified in
Princeton
Item Case
Transport and Transfer Prooesses
Table 2
Statistical properties of particle and stream motion
1 Mean velocity
of air, U, gps
2 Reynolds no. of
duct flow
3 Particle flow
rate, lb./min.
4 Particle size,
micron
5 Stream intensity,
gps.
6 4172/u
7 Scale of turbulence
of stream, 11, ft.
8 Eddy Aiffusivity,
El ft /sec.
9 Particle
intensity
10 Particle diffusivi- .0014/.0007
ty, E Ift2/sec.
11 Scale of turbulence .0016
of particles, ft.
12 Reynolds number 4.95 2.81
of particles
13 K (Ref. 10) 330 16.42 49.2
14 (12 - 172%)/ j2 -.0662 .404 .702
15 g/F, fps 161 40.5 40.5
(ref. 10)
16 F.p/
5
55
6
55
7
55
8
85
9
85
8348o
83480
83480
129000
129000
0
.393
.406
.395
250
110
lio
1.14
1.18
1.27
1.68
1.58
.0207
.0215
.0231
.0198
.o186
.0412
.0503
.0469
.0291
.0337
.0470
.0593
.0568
.0489
.0533
2.14
1.84
3.06
1.22
.98
.86
3.50
45
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1,
-,..*77?????????-? -
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:?7;
..?
Purdue
Transport and Transfer Processes
STUDIES OF HEAT TRANSFER TO GASES
AND
THE MECHANISM OF TWO PHASE FLOW
Purdue University - Phase 11
M. J. Zucrow, Project Director
C. F. Werner, B. A. Reese, Phase Leaders
D. A. Charvonia, H. Wolf, Investigators
Introduction
The research reported herein is concerned with the following two problems,
Problem 11 R1 A Study of the Heat Transfer to and from Gases with
Large Temperature Differences Between the Gas and
the Wall.
Problem 11 R3 The Investigation of Two-Phase Annular Gas-Liquid
Flow in a Vertical Tube.
The progress made with respect to each problem is reported under separate
isib-headings.
, -
47
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Discussion
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Transport and Transfer Prooesses
1,
Problem 11 R1 A Study of the Heat Transfer to and from Gases with Large
Temperature Differences Between the Gas and the Wall. The research program
discussed herein is concerned with the investigation of the heat transfer
phenomena occurring between a gas in turbulent diabetic flow and the wall of
a smooth round duct.
During the subject report period the research effort has been concerned
with the following items:
(A) Completion of the analysis of the data for cooling the gas with
the wall temperature of the duct (a) constant and (b) variable with
axial distance.
(B) Adaptation of the theory developed by Rubesin for flat plates, to
the prediction of the influence of the wail temperature gradient upon
the heat transfer to or from a gas in turbulent diabatic flow in a
circular tube.
(C) Completion of the theoretical analysis of heat transfer in the
entrance regions of smooth round ducts.
(D) Revision of the existing apparatus for conducting heat transfer
experiments with hydrogen.
The afore-mentioned items are discussed in detail in the following para-
graphs.
(A) Cooling Experiments. For these experiments, the local and the average
values of the heat transfer coefficient, Nusselt number, and Reynolds number
48
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Transport and Transfer Processes
were computed. The experiments were conducted with air and with carbon di-
oxide in a test section having L/D = 60 (see Reference 1).
Figure 1 presents the thermal entrance lengths Lia (for air and carbon
dioxide) as functions of the bulk Reynolds number for conditions where the
wall temperature was invariant with axial distance. Included in the figure
are the values of thermal entrance length (Li) predicted by the theory
described in (C). Figure 1 shows that the predicted values of thermal
entrance length are conservative. Table I summarizes the range of values
obtained for Lhi for the stated ranges of bulk Reynolds number Witeb'
TABLE I
Range of Experimental Values for the Thermal Entrance Length
(Cooling Experiments)
Gas
"Re
Air, cooling
7-12
16-25
25,000 to
CWT**
152,000
Air, cooling
16-483K-*
20,000 to
VWT
94,000
CO22 cooling
5-14
12-26
23,000 to
CWT
218,000
CO cooling
12-28
20-38***
24,000 to
127,000
The thermal entrance lengths Lla and L. are defined as the distance
n5
from the entrance to the cross section where the local heat transfer
coefficient is equal to 1.01 or 1.05 times the asymptotic value of the
heat transfer coefficient.
** CWT denotes wall temperature constant with axial distance.
VWT denotes variable wall temperature with axial distance.
*** Estimated values.
49
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Transport and Transfer Processes
The increase in the local Nusselt numbers Nub downstream from the en-
trance region is attributed to the decrease in the thermal conductivity of
the flowing gas with decrease in the local bulk temperature.
The local heat transfer coefficient decreased rapidly just beyond the
entrance section and then decreased to a substantially constant value for
x/b values ranging from 12 to 26 diameters depending upon the Reynolds number.
The average heat transfer results for the cooling experiments conducted
with air and carbon dioxide, for a constant wall temperature, were best cor-
related by evaluating the physical properties of the gases at the average
bulk temperature. Figure 2 presents the bulk Nusselt number Flub as a function
of the bulk Reynolds number Witeb for the cooling experiments. The afore-
mentioned results are correlated with a maximum deviation of + 6 per cent by
the following equation.
-8
"Nub = 0.0181 Naeb 0.
(1)
The subscript b denotes that the physical properties were evaluated at the
average bulk temperature. Including the Prandtl number to the 1/3 power in
equation 1 increased the maximum deviation of the results from the correlating
line to + 7 per
Colburn modulus
tion of + 7 per
cent. Correlation of the results presented in Fig. 2 by the
as a function of the Reynolds number yielded a maximum devia-
cent when the properties were evaluated at the bulk tempera-
ture and + 10 per cent when the properties were evaluated at the average film
temperature "flf = (Tb + Ilv)/2, where -1114'is the average wall temperature.
, - -
50
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(2) .
Transport and Transfer Prooesses
The results briefly described above are discussed in detail in Reference
(B) Prediction of Influence of Wall Temperature Gradient. Analytical studies
of heat transfer from non-isothermal surfaces (3) (4) demonstrated that the
variation of the surface temperature with distance has a significant effect
upon the heat transfer to or from the surface. A calculation of the total
amount of heat per unit width Q(W) transferred from a flat plate of length W
with an unheated starting length L to a gas flowing turbulently over the sur-
face is presented in Reference (2). The results of the afore-mentioned calcu-
lation are given by the following equation.
where
Q(W)
-w,0)
1 _ ETw2 - Ti) I1 + 1.25 L Twia x) I} (2)
? 2
/47 3 L 5
the total amount of heat transferred per unit width and
time from the heated portion of the plate.
h(11.40) the local heat transfer coefficient at the end of the
plate, x = W.
the distance from the leading edge to the end of the
heated section.
the distance from the leading edge to the point of dis-
continuity in the surface temperature,
the surface temperature at x = L.
51
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Transport and Transfer Processes
the surface temperature at x = 17.
the surface temperature at location X.
the distance along the plate, the leading edge being
the point x = 0.
1
-)11::AOr -(4.4-5r)/5r
II (1 -1! ) it
cat
.j(ft
(1 _11)(5+1) 71 -(9+5r)/5r
dll
(Vtif
(L/ x)'
(28 m + 39)/40
(7 + 28 m)/(28 m .1- 39)
a constant, the value of which is restricted to the interval
- 1/4IS m9/28. (3)
For given values of LI Mr, and Reynolds number the integrals I, 12, and the
term h(W,O) are constants. The term 1.25 L(jTiax)I2 then represents the
contribution to the total quantity of heat transferred because of the sur-
face temperature gradient; the latter was assumed to have a constant value in
the derivation. If it is assumed that the heat transferred from a gas to a
tube of length 14 with an uncooled length L is similar to C11(W) for a flat
plate, then equation 2 may be employed for predicting the influence of
aVax. Equation 2 deMonstrates that for the case of cooling (T)124.Tia)
the total amount of heat transferred from a gas to the tube wall should be
62
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Transport and Transfer Processes
larger when the surface temperature decreases with distance than if the sur-
face tenperature were constant with distance; conversely for a positive sur-
face temperature gradient the heat transferred would be less than that for
zero gradient. Figure 3 presents the results of cooling experiments con-
ducted with air in a tube having positive and negative values of a Tic), it
is seen from the figure that the experimental results are in qualitative
agreement with the trend predicted by equation 2. A choice of the constant
m = 1/7 results in better quantitative agreement between the predictions of
equation 2 and the experiments conducted with the wall temperature invariant
with distance. Figure 4 presents the experimental results (see Fig. 3) ad-
justed to conditions of constant wall temperature by assuming the heat trans-
ferred in the tube to be proportional to the quantity enclosed by the brackets
on the right-hand side of equation 2, and that 28 in = 4. Included in Fig. 4
are the adjusted results of heating experiments with Reynolds number less
than 100,000. It is seen from Fig. 4 that the theory adequately predicts the
influence of a vax for values of I71.113 less than approximately 1.6. It
should be pointed out that in applying the modified theory of Rubesin to the
heating experiments it was assumed that a Vox was constant along the tube
which is not the case. The assumption that a vax is constant appears to
be satisfactory for those experiments where Ifw/ "fb< 1.6. The experimental
results obtained with carbon dioxide under the above-mentioned conditions and
the predicted influence of the surface temperature gradient directly parallels
that illustrated for air.
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Transport and Transfer Processes
(D) Revisions to Apparatus. The apparatus for conducting heating experiments
is being revised so that hydrogen gas can be used as the flowing medium and
average wall temperatures exceeding 2000 R can be obtained. A new test sec-
tion has been fabricated of Haynes Alloy 25 tubing 0.306 inches ID and 40
diameters long. An isothermal starting length 46 diameters long is provided
upstream to the test section. It is estimated that Reynolds numbers up to
50,000 can be achieved with hydrogen gas as the heat transfer fluid. The
revision is approximately 75 per cent complete and it is anticipated that
exploratory experiments will be in progress by May 1958.
Problem 11 R3 The Investigation of Two-Phase Annular Liquid Flow in a
Vertical Tube. This investigation is concerned with the analytical and ex-
perimental study of the mechanism of the downward or "gravity" flow of a
liquid film on the inside wall of a vertical circular tube with co-current gas
flow in the core of the tube.
A report analyzing the status of knowledge on the subject is in prepara-
tion and should be ready for distribution by June 1958. The most pertinent
findings obtained from the literature review (8) are summarized below.
1. The theory proposed by Nusselt (1916) for describing the mechanics
of liquid film flow and the transfer of heat through liquid films is in-
adequate for predicting the rates of heat, mass, or momentum transfer in an-
nular two-phase flow after surface disturbances have appeared upon the inter-
face separating the liquid phase from the gaseous phase.
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Transport and Transfer Processes
(C) Theoretical Analysis of the Heat Transfer in the Entrance Region. Calcu-
lations were made of the heat transfer characteristics for air and carbon di-
oxide in turbulent diabatic flow in the thermal entrance region of a smooth
round tube. It was assumed that the flowing fluid had a fully developed
velocity profile and a uniform temperature profile at the cross section where
energy exchange was initiated. The thermal boundary layer thickness was com-
puted according to the method of Deissler (5) for both the constant heat flux,
and the constant wall temperature boundary conditions. The variations of the
physical properties of the fluid with temperature were assumed to approximate
those for air and for carbon dioxide. The velocity and temperature profiles
employed in the region between the wall and the edge of thermal boundary layer
were those calculated by Botje (6) for fully developed flow. In the region
outside the thermal boundary layer the temperature of the fluid was assumed
constant with distance from the wall and the velocity profile was assumed to
be that for adiabatic flow. The derivation of the relationship for the thermal
boundary layer thickness with axial distance, and the method of calculating
heat transfer and flow parameters in the entrance region are presented in com-
plete detail in References (2) and (7).
Figure 5 compares the results of the afore-mentioned analysis with the
experimental results, described under (A) above, for cooling carbon dioxide in
a test section having L/D = 60. Figure 6 compares the predicted and experi-
mental results for heating air. It is seen from Figs. 5 and 6 that the agree-
ment between theory and experiment is satisfactory for practical purposes.
54
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Transport and Transfer Processes
2. The increase in the surface area, due to the surface disturbances,
is insufficient for accounting for the increases in the transfer rates after
those disturbances occur.
3. Initial theoretical approaches to a solution of the problem of two-
phase flow were semi-empirical in nature and attempted to solve the problem
by neglecting the specific flow pattern.* Experimental evidence indicates
that the flow pattern must be considered in any complete solution of the
problem.
4. More recent theoretical solutions appear to yield good results for
some flow conditions but are inadequate for other. Insufficient experimental
data are available for determining conclusively the applicibility of any of
the theoretical solutions.
5. From two-phase annular flow experiments there is evidence that the
pressure drop may be correlated in a fashion analogous to that employed by
Moody for single-phase flow in rough pipes. That method has not been gen-
eralized, however, because the exact effect of the liquid flow rate is not
known.
6. Since the surface disturbances are random in nature, a statistical
approach to solving the problem would appear to be most promising. The re-
sults of such a study for the single-phase flow of a liquid film was reported
recently by von Brauer (9).
* Flow pattern - slug, bubble, mist, annular, etc.
56
Purdue
Transport and Transfer Processes
7. Most of the investigators realize that there is a need for a more
detailed description and a more thorough understanding of the surface dis-
turbance phenomena.
8. It is apparent that currently there is no general solution, either ?
theoretical or experimental, for two-phase annular flow.
The construction of the experimental apparatus has been completed. Cur-
rently the instrumentation is being calibrated, and some exploratory experi-
ments are being conducted for the purpose of obtaining experience with the
new apparatus.
Notes and References
1. Project SQUID Progress Report, 20 September 1957.
2. Wolf, H., "The Experimental and Analytical Determination of the Heat
Transfer Characteristics of Air and Carbon Dioxide in the Thermal
Entrance Region of a Smooth Tube with Large Temperature Differences
Between the Gas and the Tube Wall" (in two Parts), Ph.D. Thesis,
Purdue University, March 1958,
3. Rubesin, M. W., "The Effect of Arbitrary Surface Temperature Variation
Along a Flat Plate on the Convective Heat Transfer in an Incompressible
Turbulent Boundary Layer," NACA TN 23450 April 1951.
4. Tribus, M. and Kline, J., "Forced Convection From Non-Isothermal Sur-
faces," Heat Transfer Symposium, University of Michigan Press, 1953,
p. 211.
5. Deissler, R. G., "Analysis of Turbulent Heat Transfer and Flow in the
Entrance Regions of Smooth Passages," NACA TN 3016, October 1953.
6. Botje, J. M., Ph.D. Thesis, Purdue University, 1956.
57
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Transport and Transfer Processes
7. Wolf, H. and Zucrows H. J., "The Analytical Determination of the Local
Heat Transfer Characteristics of Gases Flowing Turbulently in the Thermal
Entrance Region of a Circular Duct with Large Temperature Differences
Between the Gas and the Duct Wall," Report No. R14,57-2, Jet Propulsion
Center, Purdue University, December 1957.
8. Project SQUID Progress Report, 1 October 1957.
9. Von Brauer, H., "Stromung und Warmeubergang ber Rieselfilmen," VDI-
Forschungsheft 457, 1956.
?
58
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Transport and Transfer Processes
1 1
?CARBON DIOXIDE
30 COOLING
? T= CONSTANT
20
15
. 10
(9 8
THERMAL ENTRANCE
(1111
L h :2 ? NReb"
I.
0
oe? 1 it.
6-0co
-?w As0.0
D 1
0 1 oi? 1 1?!............7.-,-T? 1
I 1 1 I 1
THEORY (L8) ?PRI-0.02
PR1-0.0 4
e /3---0.07
20 30 40
(a)
60 80 100
1 1
200 300
--- AIR
40 COOLING
= CONSTANT
30
20
15
10
hl 2.4 N Rebi:12
........
......
= ? 0.05
Px0.0
swam
comma.
o /3z-0.02
THEORY (L8) Q/3-0.O4
1(br) ?Pcts?o.o6
I I
20 30 40 60 80 100 200 300
BULK REYNOLDS NUMBER, FIReb X 10-3
Fig. 1 Variation of Thermal Entrance Length with Bulk Reynolds Number
and 13 for Air and Carbon Dioxide; Cooling, Constant Wall
Temperature.
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35
30
25
? 20
0
15
CO 10
n 9
8
Transport and Transfer Processes
COOLING, aTw /aX 0
L/D=60
Tb = 650 ? 1950 R
= 550 ? 1230R
? AIR
o CARBON DIOXIDE
5
lit- Nub= 0.023 FIReg?8 Flpir/3
( Npr =0.71)
? 6 PERCENT
Nub = 0.0181 NRa.8
PROPERTIES EVALUATED AT Tb
1 1 1
20 30 40 50 60 80 100 150 200
REYNOLDS NUMBER, FIReb X 10-3
Fig. 2 Correlation of Bulk Nusselt Number With Bulk Reynolds Number
for .Air and Carbon Dioxide; Cooling, Constant Wall Temperature.
60
? - -
z
?
, 1
7
Let'
rE
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30
Transport and Transfer Processes
25
? 20
1 1 1 I
WALL TEMPERATURE VARIABLE
WITH DISTANCE
COOLING
15
BULK
6
AIR VS() X "irb
R /IN R
o ?19 1350
? ?23 1700
? +12 1500
? +16 1700
5
4
AIR
10
z CONSTANT (950R)
15 20 30 40 50 60 70 80 100
BULK REYNOLDS NUMBER, NRob X 10-3
Fig. 3 The Influence of Variable Wall Temperature Upon the Nusselt
Number for Air; Cooling.
63.
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30
0
x20
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Transport and Transfer Processes
e HEATING, ()Tv/ /aX > 0
O COOLING, rw/aX < 0
? COOLING, crw /aX > 0
COR
6
4
?
? 1\14/-11=1.6
CONSTANT WALL TEMPERATURE
?(COOLING,;= 950)
1
20 30 40 60 80 100
CORRECTED REYNOLDS NUMBER, iiiReb X t0-3
Fig. 4 Variable Wall Temperature Results for Air Corrected to Conditions
of Constant ViaLl Temperature; Heating and Cooling, Properties
Evaluated at the Bulk Temperature.
62
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?
.1 1
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Transport and Transfer Processes
300
250
ca 200 _
2
tu 150
50
CARBON DIOXIDE
CONSTANT WALL TEMPERATURE
COOLING
0111=MX11
THEORY,
RUN NO.
? 288
? 282
e 292
o 268
0.030
0.034
"Rib
100,000
41111MINIEN
75,0_00
0.050 t
FIReb
103,630
79,400
II
z.0.07?
0.068
50,000
OM= 41111, mom,
I I
0.07g I "
30,000
moon
d
0.079
0
49,470
32,300_
0 2 4 6 8 10 12 14 16 18 20 22
AXIAL DISTANCE, X/D
Fig. 5 Comparison of Experimental and Predicted Values of Local Bulk
Nusselt Number for Carbon Dioxide; Cooling, Constant Wall Tem-
perature.
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Transport and Transfer Processes
AIR
CONSTANT HEAT FLUX
HEATING
0.003
0.0034
?
I I
THEORY, Nul
4 200
'15414%, I
46441*. I
I I IIMMINN.
firank3.,
I
0.0022
0.0025
RUN NO.
o 187
183
87
39
0.0037
0.004
NRei
I 199,120
NLI 1
200,000 14:1E90
?mom
7.67...40.7... ..7.1....... I 06,520
1 t t 100,006-- 1
150,000 1 1
1 1 1 1 53,800
----11-1--? 4721P-m:Irr-sir.-----
I I 4?
0.003 50,000
1
0.0030
I 1
2 4 6 8 10 12 14
AXIAL DISTANCE, X /D
16 18 20 22
Fig. 6 Comparison of Experimental and Predicted Values of Local Initial
Nusselt Number for Air; Heating, Constant Heat Flux.
64
?
Catholic University Chemical Kinetics
REACTIONS OF HYDROGEN ATOMS
Contractor: The Catholic University of America
Contract No. N6Ori-105, Task 3
Personnel: B. de B. Darwent, Phase Leader
V. J. Krasnansky, Investigator
L. J. Stief, Investigator
Introduction
In the last Semi-Annual Progress Report (April 1957), results were pre-
sented showing that the H atom produced in the photolysis of HI was "hot"
and, therefore, that the results obtained by Bates, et.al. on the reaction
of H with 02 should not be accepted without reserve. The results included
in the present report were obtained by photolyzing H2S in the presence of 02.
There is good experimental evidence that the H atoms produced in the pho-
tolysis of H2S have thermal velocities. The following simple mechanism:
H2S + hv --4 H + HS (0)
H + H2S ---- H2 + HS (1)
H + 02 --> H02* (2)
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Catholic University
H02* H +
H02* + N H02 +
assumed for the process, and leads to the identity:
?' = (41/1-0) = (k1/k2r + k3/k4mT (A)
where his the quantum yield of H2, r is pi/p21 pi being the concentration of
H2S and p2 of 02, and xis the concentration of all species. If H02* is
long lived (i.e., k3 = 0), we get
= 1 + k2/(k1r)
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02
Chemical Kinetics
(3)
(4)
Results
(B)
A plot of 1/0 against 1/r showed a considerable deviation from linear-
ity, indicating that equation (B) did not account adequately for the results.
However plots of Z'vs 1/midid provide straight lines with small but definite
intercepts, in conformity with equation (A). This suggests strongly that
the simple mechanism is essentially correct and that k3 is not negligible.
Linearity of Yvs 1/m is obtained, at constant temperature and r,
whether the variation in m was accomplished by varying pi and p2, but keep-
ing the ratio constant, or by maintaining pi and p2 constant and adding
varying amounts of CO2 to alter the total pressure. However, the intercepts
in the former case were considerably larger than in the latter. This
suggests the occurrence of another proce5s:-
2 02 (5)
H02* +
02
the inclusion of which alters the kinetics slightly to give:
66
Catholic University
= (k1/k2r 1 1- -.11511.-
k4m
Chemical Kinetics
The ratios k1/k2 and k3/k4 were measured at 500, 930 and 150? C. giving
the differences in activation energies, and k5/k4 at 50? C.
data were obtained for the ratio of rate constants:-
T. (c) C. 50 93
The following
150
kl/k2
0.060
0.137
0.171
(k1k3/k2k4) x 103(mm71)
0.395
0.765
1.45
(k3/k4) x 103 (mm71)
6.58
5.58
8.48
k5/k4
33.
It seems likely that the ratio k3/k4 is independent of temperature,
so that E3 - E4 = 0. The Arrhenius plot of ki/k2 and k1k3/k2k4 both give
activation energies of 2.8 kcal. mole-1. There is some uncertainty in the
magnitude of Ei which may be 4.88 or 7.5 kcal. mo1e-1. Hence E2 will be
2.05 or 4.7 kcal. mo1e-1. From the magnitude of k3/k4 we find that, if
reaction 4 occurs on every collision, k3 will be 1.9 x 1010 sec.-1 or
the minimum average life of H02*, will be about 5 x 10-11 sec.
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Penn State
Chemical Kinetics
HIGH TEMPERATURE REACTIONS
The Pennsylvania State University, Phase I
Dr. Howard B. Palmer, Phase Leader
Mr. Bernhard Deklau
Mr. Bruce Knox
Introduction
The objective of our work on high temperature reactions is to add to
the basic understanding of reaction rates at high temperatures. The
general procedure in this effort is to observe a gas as it undergoes very
rapid heating in a shock wave and to attempt to follow the rates of
reactions of pertinence, as they set in behind the shock front. We
have begun measurements of the high temperature dissociation rate of
gaseous NOC1. This molecule is of interest first because it probably
can decompose by two mechanisms,
2 NOC1 -32 NO + Cl, (1)
4
and NOC1 + M -*NO + Cl + M (2)
the second process presumably proceeding via the Lindemann mechanism. It
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Penn State
-
Chemioal Kinetics
is well known that process (1) occurs at low temperatures, and there are
indications
significant
data on the
in the literature that process (2) is already making a
contribution at temperatures as low as 400?K. Literature
decomposition rate extend up to 573?K, with one rough value
available at 1020?K. The second reason for interest in NOC1 is that it
is triatomic. If appreciable contribution to the dissociation rate is
made by transfer of energy from rotational and vibrational energy modes
to the 0-C1 bond, the contribution might be expected to be quite large
and should show up at relatively low temperatures. The literature data
allow an estimate to be made of the rate constant of reaction (2),
assuming second order behavior (i.e., "low pressure" behavior, in the
Lindemann scheme). The estimate is
k = 1015 exp (-30kcal/RT) cc/mole sec.
This conforms to expectations in having a large
indicative of extensive energy coupling, and an
energy below the 0-C1 bond energy, 38 kcal. It
pre-exponential factor,
empirical activation
seems that detailed
study of the rate at high temperatures should be interesting and
worthwhile.
Discussion
Our shock tube is operating satisfactorily now, and a number of
preliminary runs have been made with commercial NOC1. This is not of
adequate purity to give usable rate data, so will be further purified by
70
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0henicsal Kineiias
distillation. Calculations of shock conditions corresponding to various
measured velocities in pure NOC1 and in NOC1 diluted with argon are
being completed. Calculations of shock conditions expected from initial
pressure ratios across the diaphragm (He driver) have also been made
for guidance in making experimental runs.
From one of the preliminary runs we have made a rough estimate of
the dissociation rate and computed a rate constant (at ca. 800?K) that
appears to conform reasonably well to the above estimated rate constant
of reaction (2). It appears from this that a study of NOC1 decomposition
may be particularly worthwhile by the shock wave technique because the
rate should be fast enough at low enough temperatures for careful
examination of agreement between kinetic data from shock wave experiments
and those obtained by more conventional methods.
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Stanford
Chemical Kinetics
SURFACE-CATALYZED ATOM AND FREE-RADICAL REACTIONS
Stanford Research Institute - Phase II
Henry Wise - Phase Leader
Clarence M. Ablow
Bernard J. Wood
Introduction
The heterogeneous interaction of labile species such as atoms and free
radicals is associated with various aspects of combustion and propulsion.
In this investigation, the surface activity of various solid surfaces for the
recombination of atoms is quantitatively examined.
Discussion
The experimental procedure employed in the measurements of the activity
of metallic and nonmetallic surfaces for the recombination of atoms has been
described in the previous semi-annual progress report (dated October 1, 1957).
73
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Stanford
Chemical Kinetics
The dynamics of heterogeneous radical reactions in a system such as employed
in our measurements have been examined from a theoretical viewpoint. This
theoretical analysis includes the effects of radial and longitudinal dif-
fusion in a cylinder of finite length containing "atom sinks" of different
relative magnitude. The mathematical treatment is contained in a forthcoming
Squid report.1
The measurements of surface activity have included the interaction of
hydrogen atoms with transition metals. In particular, the recombination
coefficients y of the first series of transition metals have been studied.2
The results of our determinations are summarized in Table I, which includes
also several other surfaces of interest. It is to be noted that in the case
of a very active surface such as platinum, one in every four collision leads
to recombination and the formation of a hydrogen molecule. For a less active
transition metal such as titanium, the recombination coefficient is reduced
by a factor of about 2.5. Pyrex glass exhibits a relatively low value of y.
The experimental measurements are being extended to other metallic and non-
metallic surfaces including semiconductors.
Notes and References
1. Henry Wise and C. M. Ablow, "Diffusion and Heterogeneous Reaction I. The
Dynamics of Radical Reactions." (Squid Report, March 1958)
2. The recombination coefficient y is defined as the ratio of the number of
atoms striking the surface and reacting to the total number of atoms hit-
ting the surface.
3.3.33rw.??????.er?.3
74
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Chemical Kinetics
Table I
RECOMBINATION EFFICIENCY OF VARIOUS SURFACES FOR HYDROGEN ATOMS
Surface Ti V Cr Mn Fe Co Ni Pb Cu Pyrex
Recombination 0.10 0.15 0.16
Coefficient
0.22 0.17 0.18 0.18 0.24 0.19
Percent 27 35 39 40.1 39.7 39.5 4o 44
"d" character*
*L. Pauling, Proc. Roy. Soc. A196, 343 (1949)
.
75
7.5 x 10-4
ON.
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Atlantic Research
Combustion Phenomena
STRUCTURE AND BURNING MECHANISM OF LAMINAR FLAT FLAMES
Atlantic Research Corporation - Phase 3
R. Friedman, Phase Leader
R. G. Nugent
Introduction
The program to date has been centered on the problem of measuring
temperature and composition gradients in low-pressure premixed carbon mon-
oxide flames with small known amounts of either hydrogen or water vapor
present. The ultimate objects are to gain understanding of the rate-
controlling process in the oxidation of carbon monoxide under flame
conditions, and to develop generally applicable techniques for measuring
flame reaction rates.
The work naturally divides itself into three sections, the obtaining of
traverse data, the primary analysis of these data to yield heat-release and
reaction rates, and the final analysis of these rates to define the under-
lying mechanism. Progress in each of these sections will be briefly
described.
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Atlantic Research
Experimental
Combustion Phenomena
Flat flames are stabilized on a burner of 25-cm diameter, at pressures
of the order of 20-50 mm Hg abs. Suitable flow-metering, ignition, and
vacuum-pumping equipment is utilized. Flame and probe positions are
measured through a window with a traveling telescope. The probe may be
moved with 6 cm of travel along the burner center-line, by means of a
traverse mechanism. Two types of probes are used, a thermocouple probe
made of 13-micron wire and a sampling probe consisting of a quartz tube
with capillary tip. Other instrumentation includes a precision potentio-
meter for the thermocouple and a gas-handling system and mass spectrometer
(Consolidated Electrodynamics Corporation, Model 21-620) in conjunction with
the sampling probe.
To date, traverses of both temperature and composition have been made in
two lean CO-02-H2 mixtures, one of which was adjusted to be 142?C hotter
than the other, and two lean CO-02-H20 mixtures, each at the same temperature
but with differing H20 contents. In all cases, the pressure was 30 mm Hg.
Some exploratory tests have been made with rich mixtures and at other
pressures, but no data have been obtained.
Discussion
From composition-traverse data, the rate of disappearance of carbon
monoxide is obtained by suitable mathematical procedures which take into
account the diffusion flow. The results may most conveniently be expressed
in terms of a first-order decay constant k for the rate of disappearance of
carbon monoxide in the "tail" of the flame; k comes out to be of the magni-
tude 200-300 reciprocal seconds for flame temperatures of the order of
1800?K.
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Atlantic Research Combustion Phenomena
An independent way of obtaining values for k is by analysis of the
temperature distribution to obtain a heat-release rate, and then to convert
this to a reaction rate by means of the known heat of reaction. Agreement
better than a factor of two has been obtained between the two methods for
several mixtures.
Certain trends of interest may be discerned from the results. The most
striking is the comparison of reactivity as determined above in a carbon
monoxide flame with the reactivity as deduced from the magnitude of the
burning velocity of that same flame. The reaction in the "tail" of the
flame seems to be an order of magnitude slower than the reaction governing
the burning velocity, even after allowance is made for the concentration
level of carbon monoxide on the basis of a reaction first-order with
respect to carbon monoxide.
A second interesting finding has to do with a comparison of two lean
mixtures of the same flame temperature, one containing three per cent
hydrogen and the other, three per cent water vapor. In the former, sampling
shows that the hydrogen is converted to water early in the flame, as one
would expect, but the rate of carbon monoxide "clean-up" in the "tail" of
the flame is much faster in the hydrogen flame than in the water-vapor
flame, which is unexpected.
A detailed discussion of these findings is presently being prepared as a
Technical Report. Future plans call for study of rich mixtures, to find
out whether the reaction is really first-order with respect to carbon
monoxide, and study of the relative intensity of light emission from the
initial highly luminous part of the flame (which presumably controls the
flame speed) and the much less luminous "tail" of the flame in which the
last of the reaction occurs.
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Bureau of Mines
Combustion Phenomena
RESEARCH ON HIGH PRESSURE COMBUSTION
United States Department of the Interior,
Bureau of Mines, Region V
Division of Explosives Technology
Pittsburgh, Pennsylvania
Phase 1
Phase Leaders: J. Grumer (1R1), H. G. Wolfhard (1R2)
Investigators: E. B. Cook, T. A. Kubala, M. Vanpee
Introduction
This program seeks to advance the understanding of combustion of explo-
sive gas mixtures. (1) In continuation of established work, burning
velocities, peak pressures, end pressures, chemical composition of the burned
gas, and expansion ratios are being measured at elevated pressures and tem-
peratures by means of a spherical vessel method. (2) Ignition phenomena are
studied which are relevant to the flame-holding of ramjet burners, where
fresh cold fuel-air mixture is continuously reignited behind the baffle in
contact with hot burned gases.
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Discussion
---------- NM
Combustion Phew:nem
Problem 1R1 - Determination of Standard Burning Velocities and Expansion
Ratios
(1) Burning velocities and their pressure dependence - The immediate
interest is in the influence of elevated initial pressure and later of initial
temperature on the propagation of spherical laminar flames in a closed vessel.
To facilitate this study, a new 8-inch I.D. stainless steel spherical vessel
is being constructed to replace the present 12-inch I.D. iron vessel which
can be operated only up to about 470 p.s.i. peak pressure. The main sections
of the new equipment have been cut. The pressure rise history during combus-
tion will be measured in the new vessel by means of a transducer. Recent ex-
periments with methane-air mixtures in the 12-inch I.D. vessel have shown good
agreement between pressure rise data taken by means of the transducer and the
heretofore employed mechanical-optical system based on the deflection of a
wide diameter diaphragm. New data taken with 10.5 percent methane-air mix-
tures in the range of 1-4 atm, initial pressure have yielded burning velocity
values in good agreement with published values for stoichiometric methane-air
mixtures (1). The pressure dependence of the burning velocity of the 10.5
percent methane-air mixtures corresponds to a pressure exponent of minus 0.36
and closely parallels the reported pressure dependence for stoichiometric
mixtures at these elevated initial pressures. The data in reference 1 were
obtained with a 10-inch spherical vessel. The close agreement between the
data from the 10-inch and the 12-inch vessel indicates that a vessel diameter
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Bureau of Mines
Combustion Phenomena
effect is not likely to complicate future work with the 8-inch I.D. new
vessel under construction.
Other measurements were made with this slightly rich methane-air mixture
at initial pressures in the range of 1-4 atmospheres. These were peak pres-
sures, end pressures after cooling of the burned gases to initial temperature,
and analysis of the composition of the burned gas. The end pressures and
chemical composition of the burned gas indicated that the water-gas shift was
being followed as the burned gases cooled to room temperature. The computed
equilibrium temperature for the water-gas shift was in the neighborhood of
1200-15000 K. in runs where the theoretical flame temperature averaged about
2200? K.
(2) Expansion ratios - This laboratory has for some time been concerned
with the accuracy of the thermodynamic
pressure rise and flame growth data to
been approached through examination of
assumptions involved in converting
burning velocities. The problem has
existing theory and experimental
measurements of expansion ratios. Particular attention was given to the re-
lation between the pressure rise and the fraction of charge burned as the
combustion wave traverses the vessel contents. It is now clear that the
heretofore employed expression relating these two is inexact. In 1917, Flamm
and Mache (2) derived the relation between the pressure rise and the fraction
of charge burned as being
RTi(Pe - P)
1 - n -
Pi [RTu .1.11t1 + K(ib - 1)]
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Bureau of Mines Combustion Phenomena
In equation 1, n is the fraction burned, R is the gas constant, K is a con-
stant, / is the specific heat ratio, T is the temperature, P is pressure,
and the subscripts i, u, b and e indicate the initial, ambient, burned and
end states of the combustion process. Later, the assumption was made that
Ti may be substituted for Tu, changing equation 1 to equation 2 (3, 4).
- P - Pi
n (2)
Pe Pi
The substitution was justified by noting that it changed the value of 1 - n
very little. However, for an error of y in 1 - n, the error in n is
(y/n)(1 n). When measuring burning velocities, small values of n are
employed and errors in n result in about equal errors in the burning velocity.
In this way, when n 0.03, a change in 1 - n of 0.3 percent will change n
and the burning velocity by about 10 percent.
Instead of the above substitution, Tu has been evaluated when P/Pi? 1.1,
using the information that the rise in pressure in the unburned gas is due to
the adiabatic compression of the unburned gas by the expansion of the burned
gas formed. In this way, equation 1 has been transformed into equation 3,
with an estimated error in n of less than one percent.
P - Pi
n
Pfeu(E - 1)
Here, E N (mbiTbi)/(miTi) is the expansion ratio for constant pressure
burning at PiTi; m is mols.
(3)
Equations 2 and 3 for the fraction burned are in the ratio to each other
of about the ratio of the specific heat ratios of the unburned and burned
84
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Bureau of Mines
Combustion Phenomena
gases--a factor of about 1.1. This 10-percent difference is about the differ-
ence in the burning velocity that one gets from these two expressions. The
substitution of equation 3 for equation 2 has now been justified both by
analytical mathematics and experimentation. The details of these efforts
have been included in a new publication from this laboratory on spherical
vessel combustion (5).
Problem 1R2 - Study of High Pressure Combustion - The work on high
pressure flames was discontinued mainly because A. Strasser, who conducted
the experiments of this phase of the program, was no longer available and
partly because the ignition work (see below) proceeded more satisfactorily.
Dr. M. Vanpee has joined the program.
The ignition of methane-nitric oxide mixtures by pilot flames was first
investigated. The results will not be discussed here as they are now avail-
able on microcards (6). Supplementary measurements concerning "spontaneous
ignition temperatures" of nitric oxide-fuel mixtures are also available on
microcards and have been published (7).
As a next step, hydrocarbon-air mixtures were ignited by jets of hot
gases which were heated in ceramic furnaces. It was found that the "hot-gas
ignition temperature" is a well-defined value which depends on mixture
strength and jet diameter, but only little on jet velocity as long as the
flow is laminar. No correlation seems to exist between spontaneous ignition
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Bureau of Mines
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ta.e.
Combustion Phenomena
temperature and "hot-gas ignition temperature." A paper has been written on
this subject which is available on microcards (8).
The research now in progress is aimed at a closer understanding of the
hot-gas ignition process and its correlation with the problem of flame-holding
in ramjet burners. The influence of inhibitors on hot-gas ignition has been
investigated. It was found that iron carbonyl and tetraethyl lead have no in-
fluence on hot-gas ignition, although they influence spontaneous ignition
greatly. Methyl bromide, which influences flame propagation, also increases
the temperature of the hot jet necessary for ignition. The close parallel
between hot-gas ignition and limit flame temperatures is now further investi-
gated and limit flame temperatures are measured with a spherical diffusion
flame arrangement. It is planned to measure hot-gas ignition temperatures
also at reduced pressures and to study the kinetic processes in detail.
Notes and References
1. D. Smith and J. T. Agnew, "Sixth Symposium (International) on Combustion,"
Reinhold Publishing Corp., New York, 1957, p. 83.
2. L. Flamm and H. Mache, Wien. Ber., 126, 9 (1917).
3. B. Lewis and G. von Elbe, "Combustion, Flames and Explosions of Gases,"
Academic Press, Inc., New York, 1951, pp. 448-59, 473-79, 656-64.
4. B. Lewis and G. von Elbe, J. Chem. Phys., 2, 667 (1934).
5. J. Grumer, E. B. Cook, and T. A. Kubala, Considerations Pertaining to
Spherical Vessel Combustion. Under review.
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Bureau of Mines
Combustion Phenomena
6. H. G. Wolfhard and D. Burgess, The Ignition of Combustible Gases by Flames.
Combustion and Flame, in print. Project SQUID Technical Report BUM-22-P,
August 1957.
7. H. G. Wolfhard and A. Strasser, J. Chem. Phys., 28, 172 (1958). Project
SQUID Technical Report BUM-23-P, August 1957.
8. H. G. Wolfhard, The Ignition of Combustible Mixtures by Hot Gases,
Jet Propulsion, in print. Project SQUID Technical Report BUM-24-P,
December 1957.
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Cornell
Combustion Phenomena
INVESTIGATION OF FLAME PROPAGATION AND STABILITY
WITH PARTICULAR REFERENCE TO THE INTERACTION BETWEEN FLAME AND FLOW
Cornell Aeronautical Laboratory, n . - Phase 2
G.H. Markstein, Phase Leader
L.M.Somers, H.M.Prestan
Introduction
This investigation is primarily concerned with mutual interactions
between flow disturbances and flames. Flame structure is studied in the
presence of artificial or spontaneous flaw disturbances, comprising fluctua-
tions of a more or less random nature as well as pipe resonance oscillations
and pressure waves. The experimental methods include still, motion picture,
and streak camera photograplly of flame structure, sampling of burned gases
for chemical analysis, oscillographic recording of pressure and radiation
transients, use of ionization probes for timing of flame propagation, and
smoke or particle tracer techniques of flow visualization. Concurrently,
the interaction of flow disturbances with flames is being investigated-by
methods of perturbation analysis.
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Cornell Combustion Phenomena
Discussion
Work on preferential diffusion effects and other transport effects
across flow lines in curved laminar flame fronts has been started. Steady,
two-dimensional cellular flames are being used thus far as a convenient
system for this study. A slot burner previously developed for obtaining
these flames1'2 was slightly modified in order to facilitate int-oduction of
a sampling probe into the flame from the burned-gas side. One modification
consisted of reducing the height of a flame enclosure, used for preventing
entrainment of air into the burned gas, to 3/4 in. The other one consisted
of introducing two steel wires of 1/16 in. diameter into the nave near the
flame base, for the purpose of preventing the tendency of the flame cells for
irregular lateral motion. These wires were mounted on supports that could be
moved along the slot and clamped in any position. By placing one of these
wires on either side of the sampling probe, the cells near the probe could
be completely immobilized.
Two types of probes were tried for sampling of the flame gases. Quartz
capillaries similar to those used by others3,4,5 were first employed. While
otherwise satisfactory, they tended to close off gradually when exposed to
the hot flame gases. Recently an uncooled stainless steel capillary pinched
off at the end into a narrow slit has been tried. This probe appears to re-
main open indefinitely as long as it is not exposed to partially burned
oxidizing gases. At present both probe types are being used and their rela-
tive merits are being evaluated. The probes are mounted on a slide compound,
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Combustion Phenomena
so that traverses along the wavy-flame front in the burned gas as well as
through the flame front in a normal direction could be carried out.
The analysis of the gas samples is carried out by gas chromatography.
Molecular sieve SA is used as column material for the separation of
H2, N20 02 + Al CO and CH. 02 to c4 hydrocarbons and CO2 are analyzed with
a silica gel column. The analysis of water is carried out with a partition
column of 2-aminobiphenyl on firebrick. Except for the analysis of water
concentrations the gas samples withdrawn by the probe are dried and pumped
into glass sample flasks at a pressure of 200 mm Hg, and are then pressur-
ized with mercury for introduction into the chromatograph at atmospheric
pressure.
A special technique was developed for analysis of water, in order to
overcome absorption and adsorption difficulties. For this purpose the gas
sample is pumped continuously from the probe through the sample valve of the
chromatograph at a pressure of 200 mm Hg. The connecting hoses and the
sample valve itself are heated electrically-to about 1200 C for Preventing
condensation and adsorption. The temperature of the sample volume on the
sample valve is measured with a thermocouple.
As a consequence of a highly nonlinear partition isotherm, water in
small concentrations moves much slower through the chromatograph column than
at higher concentrations. As a consequence, the chromatogram peaks exhibit
a steep rise and very gradual drop, and moreover, consecutive peaks corres-
ponding to samples of the same water concentration taken at constant time
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Combustion Phenomena
intervals tend to increase in height and area and approach constant values
only asymptotically. Therefore, several samples (usually at least five) are
taken at eight-minute intervals until the peaks become reasonably constant.
Calibration of the chromatographs is carried out by means of prepared
gas mixtures. The mole fractions of the components of the calibrating mix-
tures were chosen close to those to be encountered in the flame gas samples.
The calibration procedures are in every respect identical with those for
analysis of the unknown gas samples. In particular, calibration for water
vapor is carried out under conditions of steady flow through the sample
valve at 200 mm Hg pressure and about 1200 C.
Thus far, measurements of gas composition were carried out an propane
and n-butane flames. The equivalence ratio was about 1.50 in both cases.
The results obtained by sampling along the flame front about 1.2 mm down-
stream of the luminous region showed definite shifts of composition between
the ridge and the valley of the flame structure. As expected on the basis of
the preferential diffusion hypothesis61 the carbon-oxygen ratio was somewhat
higher at the ridge, and somewhat lower at the valley, than that of the un-
burned gas. This shift of composition wass however, rather small; the total
change between ridge and valley was about five per cent. The oxygen-nitrogen
ratio remained entirely unchanged, within the limits of accuracy of measure-
ment. Carbon-hydrogen ratios tended to be too large, both at the ridge and
at the valley, compared to those of the fuels, an effect which is as yet
unexplained and is being further investigated.
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Combustion Phenomena
The most pronounced effect, however, was an apparent shift of the water-
gas equilibrium, CO2 + H2 Z--'" CO + H20, between the ridge and the valley,
corresponding to a temperature change from about 1800? K at the valley to
about 2000? K at the ridge in the case of the butane flame. A similar ob-
servation had been made previously by Jost 5 on polyhedral benzene flames. It
is planned to measure the temperature distribution in the burned gas by means
of fine-wire thermocouples, in order to determine whether the observed effect
is due to real temperature changes or to nonequilibrium conditions.
Preliminary results of traverses normal to the flame front at a ridge
and at a valley showed the usual presence of pyrolysis products of the hydro-
carbon fuel in the expected sequence. The differences between the composi-
tions at the ridge and at the valley were not very pronounced, the most
notable one being a higher maximum of acetylene mole fraction at the ridge
than at the valley.
Work on pressure wase flame front interactions has been continued.
Previous studies7 dealt with the effect of shock waves on laminar flames
of roughly hemispherical shape, so that the characteristic dimension of
their structure was the width of the combustion chamber. A two-dimensional
periodic structure of smaller scale was impressed on the flames in recent
work, by passing them through a grid of parallel wires. The response of
this structure to shock wave interaction agreed qualitatively with that pre-
dicted by the analysis of modified Taylor instability 8. Moreover, the dis-
turbance velocity amplitude predicted by the analysis from the known ratio
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Combustion Phenomena
of initial distortion amplitude to wavelength, the flow velocity behind the
incident shock wave, and the density ratio across the flame front, agreed
within 20 per cent with the velocity amplitude deduced from the observed rate
of change of flame front deformation.
The results of this work showed further that while an initial period of
about 0.3 milliseconds after passage of the shock wave was dominated by the
small-scale features of the flame structure, the large-scale flow distur-
bances that correspond to the overall hemispherical shape of the flame came
increasingly into play later on. A rough dimensional analysis was carried
out for correlating this result and previous results obtained in the absence
of small-scale structure. For this purpose, a dimensionless parameter 614
was computed, where S is a characteristic response time, U the flow
velocity behind the incident shock wave and L a characteristic length. In
the earlier work, the radiation emitted by the flame had been recorded, and
the time 6 was taken as the interval between the beginning of the inter-
action and the instant of imodimmn radiation.
The width of the combustion chamber was
length. The parameter 6U/L_ was found to
over a range of incident-shock pressure
the work with small-scale disturbances,
estimated from spark photographs; here,
regarded as characteristic
vary by about I 20 per cent
ratios between 1.16 and 1.61. For
the interval C5
the wavelength of
could only be
the initial flame
distortions was regarded as characteristic length. For this case, the
parameter 8 u/4..
was about half that for the large-scale disturbances.
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Combustion Phenomena
The correlation is thus not very good, but may provide a means for estimating
the response time of flames of given structure during shock wave interaction.
The present correlation was obtained with the same combustible mixture and
under similar experimental conditions.
It is planned to study the dependence
of the dimensionless parameter on density ratio across the flame front and on
other variables.
Work on another case of flame front-shock wave interaction has been
started in which vortex formation is the most prominent feature. In this
case the gas mixture was ignited in the center of the combustion chamber so
that the flame front initially was approximately spherical. Interaction of
the shock wave with this flame transformed it into a relatively smooth
vortex ring and a very-fine grained turbulent burning zone in the axial
region. As in the case of interaction of shock waves with helium jets or
spheres9, the displacement of the vortex ring by the shock wave exceeded that
. -
derived from one-dimensional theory, but was smaller than that computed on
the basis of the full buoyancy effect for the density ratio across the flame
front.
A brief account of the recent work on shock wave-flame front interaction
has been included in comments to be presented at the Third AGARD Combustion
and Propulsion Colloquium.
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References
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Combustion Phenomena
1. Markstein, G.H. and Somers, L.M., J. Chem. Phys. 21, 941 (1953)
2. Markstein, G.H. and Schwartz, D.,
Proceedings of the Gas Dynamics
Synposium, p. 83. Northwestern University, Evanston, Ill. 1956
3. Friedman, R. and Cyphers, J.A.1 J. Chem. Phys. 23, 1875 (1955)
4. Prescott, Rol Hudson, R.L., Poner, S.N., and Avery, W.H.,
J. Chem. Phys. 22, 145 (1954)
5. Jost, W. and Krischer, Boy Z. Physik. Chem. (N.F.) 398 (1955)
6. Maaton, J., von Elbe, Go, and Lewis, B., J.Chem.Phys. 22, 153 (1952)
7. Markstein, G.H., Sixth Symposium (International) on Combustion p. 387.
Reinhold, New York 1957
8. Markstein, G.H., J.Aero.Sci. 2h, 238 (1957)
9. Project SQUID Semi-Annual Report, 1 October 1957, p.1-6
96
Delaware
Combustion Phenomena
INVESTIGATION OF THE BASIC PROBLEMS
ASSOCIATED WITH GASEOUS COMBUSTION
University of Delaware - Phase 2
K. Wohl, Phase Leader
R. H. Atalla, G. M. Cameron, J. M. Douglas
A. L. Goldstein, D. S. Hirshfeld, R. W. Miller,
P. J. Simonetti, K. W. Sub
Introduction
The objective of this study in to obtain information on
the processes occurring in laminar and turbulent gaseous flames.
The work has been divided into three main problems: Problem
2R1: An investigation of premixed turbulent flames burning
above tubes. The approach is to determine local turbulent
burning velocities and rates of burning by chemical analysis
and measurement of pitot pressure, and to observe flame
structure and behavior in more detail by taking time-photographs
of flames at various wave lengths, instantaneous photographs
and high speed motion pictures. Problem 2R2: An investigation
of premixed turbulent flames burning in ducts. Purpose and
approach are similar to those of problem 2R1. Problem 2R3i' An
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Delaware - Combustion Phonationa
investigation of the structure and kinetics of laminar flames
at various pressures by taking spectrophotometric traverses
through flat flame fronts at wave lengths ranging from the near
infrared (5.7?) to the ultraviolet (0.3 ?).
Discussion
Problem 2R1 - A Study of Turbulent Flames Burning. Above
Tubes. The optical study of the open turbulent flame has been
continued. The flame was a stoichiometric butane-air flame
burning from a 1-inch tube at an average cold stream velocity
of 60 ftifsec.and was stabilized by a ring-shaped pilot flame
at the tube rim. In (1) it had been reported that the turbu-
lence of the approach stream had a strong effect on the
separation of the maxima of the CC- and CH-radiation, indicating
that at high degrees of turbulence, especially in the upper
-sections of the flame, the wrinkled laminar front was not the
appropriate model of a turbulent flame. Similar observations
have now been made with the CO- (or continuous background)
2
radiation. The maximum of the latter appeared, at higher de-
grees of turbulence, prior to the maxima of CC- and CH-radi-
ation, which is neither the case with laminar flames nor with
enclosed turbulent ones (though in some of these flames the
98
Delaware Combustion. Phenomena
points of incipient radiation are in this order (see below)).
The intensity at the maxima of CC-, CH- and C0-radiation
2
decreased with increasing flame height corresponding to a
widening of the flame zone with height. At low turbulence
(wrinkled flame front) the decrease was linear and was the same
for all three types of radiation. At higher turbulence the be-
havior was less uniform. Measurements at these conditions were
extended beyond the points at which the various radiation
maxima occurred in the axis. At these points a sharp drop of
the individual radical radiation set in as may be expected.
The radiative flux emerging from the total flame was
measured with a Photronic Cell at wave-lengths characteristic
of the three radicals mentioned and of the infrared water vapor
radiation. All of these types of radiation decreased by
roughly 27% on passing from low turbulence via medium to high
turbulence. It is intended to check by chemical analysis
whether this is due to flame quenching by entrained air or to
an influence of turbulence on the chemical mechanism of
combustion (2).
Experiments are under way with two-dimensional open turbu-
lent flames burning above rectangular burners between two
quartz plates. One of these flames forms an upright wedge
which is held at two sides of the burner rim, the other one
forms an inverted wedge which is held on a slit pilot flame
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Dela:wars Combustion Phenomena
across the opening of the duct. The former flame type will
serve to check the effect of burner dimensions on the flame for
the case that the scale of turbulence is kept constant by the
use of grids.
Problem 2R2 - A Study of Turbulent Flames Burning in Ducts.
The flame studied is a propane-air flame burning in a 2 inches
x 1.5 inches rectangular duct of 10 inches length from a flame
holder placed between the center lines of the 2-inch walls
which consist of quarts. The velocity was 60 ft./sec.; the
composition was varied from a fuel equivalence ratio of 0.87 to
1.21; the turbulence of the approach stream was either about
or about 9%. In (1) the points of incipience of the CH-,
CC- and H2 radiation, and the points of MAXiMUM slope of the
H20-radiation and of maximum CH- and CC-radiation in the cross-
sections of the duct, had been reported. It was concluded from
the large distances between these points that these flames
burned by way of distributed reaction zones, and it was con-
eluded from the difference between the order of these points
and those in the laminar flame that the kinetic mechanism of
turbulent burning differs in some respects from that of
laminar burning.
The observations of the C0*-radiation fit well into this
2
general scheme: In laminar flames the order of incipient
radiation is always 4, CC, CH, in turbulent flames CH, COS,
100
Delayer e
Combustion Phenomena
CC except for rich turbulent flame at large distances from the
flame holder where the points of incipience of CC and COI
coincide. The order of the maxima of radical radiation in
laminar flames shiftsfram CC, CH, CO* for lean mixtures gradu-
ally to COI', CC, CH for very rich mixtures. In turbulent
flames the order is as follows:
lean
low turbulence CH, CO* ' CC
2
high turbulence CO*' CH, CC
2
stoichiom. and rich
CH, CC, CO*
2
CC
on the average CH
CO*
2
It can be seen that the transition from lean to rich mixtures
shifts the C0-maximum in laminar and in turbulent flames in an
2
opposite direction, and that an increase of turbulence shifts
the C0*-maximum in an upstream direction.
2
Preparations for investigating turbulent flames in a
20-inch duct (as compared with the 10-inch duct presently used)
are completed. The Perkin-Elmer Vapor Fractometer needed a
number of further improvements of which a built-in thermo-
regulator is outstanding. Sensitivity and reproducibility are
satisfactory now. The flame in this burner will be studied
with all the tools developed (chemical analysis, pitot and
static pressure measurement, filter photography and direct and
-schlieren high-speed motion photography.)
101
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Delaware
Combustion Phenomena
Problem 2R3 - Spectrophotometric Traverses Through Flame
Fronts. The aim of this project is to follow the radiation in-
tensity due to various emitters while the stream of a combustibla
gas mixture passes through a steady flame zone. The arrangement
used for this purpose is a horizontal flat flame front burning
above a cooled porous metal plate at various pressures. It is
viewed edgewise by the spectrophotometer and can be shifted nor-
mal to the optical axis. The average thickness of the flame
zone seen by the instrument has been made for some purposes as
maall as 0.09 MIC,
Measurement of radical radiation which so far had been
carried out at 1 and 0 atm. has been extended to 1/6 atm. If
the pressure dependence of the NIAXiMUM radiation intensity of
the chosen band peeks (which is found at some point in the re-
action zone) is expressed by the equation I k pn it may be
stated that between 1 and 1/6 atm. the exponent n for CH,
00 and OH has a value below 1 while for CO* n is found to be
2
1.3. The higher value of the latter exponent is to be expected
since the continuous 002-radiation is proportional to a
collision number while the banded radical radiation is pro-
portional to a concentration. Also the mean width of the zones
of radical radiation has been measured. The pressure exponents
for the width lie between 0.8 and 1.1. The experiments are
being continued, e.g. with the purpose of obtaining decay-curves
,
- _
102
Delaware
Combuatiesa Phew:wens
of radical radiation at 1/6 atm.
Measurement of the infrared CO2-radiation with the help of
a lead telluride cell has started. Quantitative evaluation of
the data requires a standardized tungsten ribbon lamp with a
sapphire window. Delivery of this lamp was delayed far beyond
expectation but is expected very soon.
References
(1) Semi-Annual Progress Report, Project Squid, October 1,
1957, p. 90.
(2) R. R. John and M. Summerfield, Jet Propulsion 27, 169
(1957).
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?-?
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L.,
?Orrn.
- ? _
mtlerY. 'IC
r".7?..
4.7 .41 - t.
Experiment, Inc.
Combustion Phenomena
BURNING VELOCITY, FLAMMABILITY LIMITS, AND
IONIZATION IN FLAMES
Experiment Incorporated - Phase I
I. R. King and W. E. Meador, Jr., Phase Leaders
Introduction
This investigation is concerned with (a) obtaining accurate determina-
tions of the lean flammability limit and burning velocities near this limit,
(b) learning more about the anomalous behavior of carbon disulfide-air
flames, and (c) calculating the theoretical reasonableness of certain ele-
mentary ion-producing reactions.
Discussion
Problem 1R1 - Burning Velocities and Flammability Limits. This phase of our
program was initiated on October 1, 1957, and is concerned with obtaining
105
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r:1
1)
[
?:1
'?
"11
Experiment, Inc.
Combustion Phenomena
accurate determinations of lean flammability limits and burning velocities
near these limits. Justification for such an investigation lies in the wide
discrepancy found in existing limit data and in the almost complete lack of
burning-velocity data at and near the lean limit. The method of investigation
utilizes the flat-flame burner technique previously used in our ionization
work. Since this type of burner produces a plane, flat, stationary flame,
floating in space, out of contact with any surfaces, it is ideal for investi-
gating limits and burning velocities near these limits. The burning velocity
is determined by simply measuring the diameter of the flame (usually from
several different points), using a cathetometer or traveling telescope) and
the total flow of gases to the burner. The limit of flammability is ob-
tained from a plot of burning velocity versus composition and is taken as the
last point (on the lean side) at which it was possible to stabilize a flame.
With most of the fuels tested to date, this occurs at a burning velocity of
about 4 am/sec. Whether or not this is the true limit, or simply an apparent
limit due to our inability to stabilize flames at velocities much lower than
this, is still a point of debate. However, some flames (CO-air for example)
'have been stabilized at velocities as low as 3 am/sec.
In determining the limiting fuel-air composition, it is necessary to
correct the measured values for the preheating effect. As the gas-air mix-
ture passes through the burner tube, it is heated to some extent by the
screens and walls of the burner so that the limit measured is for an elevated
temperature. In order to compare these limits with those in the literature
(normally given at roam temperature) it is necessary to correct the
measured values for this preheating effect. White (1) has shown that when a
106
= -77"Vr?-,...,????*??????????
r ? ? , ? ,`""7.
Experiment, Inc.
Combustion Phenomena
gas is preheated, the limit is lowered by an amount equal to the amount of
additional fuel that would be required to raise the temperature of the gas-
air mixture from ambient to the preheat temperature.
Similar observations
have been made by Egerton and Thabet (2). Since previous flat-flame burners
used a corrugated matrix rather then screens to produce 1Rminfir flow, the gas
was preheated to a greater degree than in the present investigation, thus
necessitating the use of a larger preheat correction. In this investigation
it has been found that for all fuels used to date, the preheating effect
amounts to only about 50?C.
A comparison of lean limits obtained to date in this laboratory and else-
where are shown in the following table.
preheat.
All values have been corrected for
Method
Lean Limit, volume percent
Propane
Methane
Tube (3)
2.37
5.26
Flat Flame
Egerton and Thabet (2)
2.01
5.1
Badami and Egerton (4)
1.89
5.31
Experiment Incorporated
1.91
5.15
In most cases, values obtained using the flat-flame burner technique are con-
siderably lower than those using the conventional tube method.
Burning-velocity curves in the range of 4 to 10 cm/sec have also been ob-
tained for these fuels and compared with corresponding values extrapolated
from existing burning-velocity data obtained using other methods. Since the
lowest burning velocities obtainable using other methods is only about 20 to
25 am/sec, the necessary extrapolation covers a fairly wide range and so is
107
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Experiment, Inc.
Combustion Phenomena
not very definite. However, the agreement is quite good, and the present
points do help to define the complete burning-velocity curve.
The effect of moisture on the lean flAmmAbility limit and burning ve-
locity of CO-air flames has also been investigated. For very dry mixtures
(Matheson premixed air) a lean limit value of 17.3% CO in total mixture at a
burning velocity of 3.15 am/sec was obtained. With 0.18% H20, the lean limit
dropped to 15.3% CO at a burning velocity of 3.66 aq/sec, indicating that for
this fuel the lean limit is very sensitive to minute traces of water vapor.
Burning velocities show a similar effect, that is, an increase with increas-
ing moisture content.
In some of our previous work it was observed that carbon disulfide
flames are also quite sensitive to minute traces of water vapor, although in
this case water acts as an inhibitor rather than as an additive. Additional
tests have shown that these flames are quite sensitive not only to water va-
por but to many other hydrogen-containing compounds as well. Some prelimi-
nary results, obtained for upward propagation in a 5-cm-diameter tube, are
shown below;
Additive
% CS 2 Necessary for Propagation
0.0%
1.30
0.13% H2
1.52
0.50% H20
1.75
0.13% C2H4
3.60
0.34% C2H4
3.58
0.13% C2H6
3.34
Part of our program is concerned with making accurate determinations of
the effect of water vapor on the burning velocity and flammability limits
108
;
Experiment, Inc. Combustion Phenomena
of the C32-air flame. Because this flame is one of the most difficult of all
flames to work with because of its great sensitivity to wall or surface
effects, the flat-flame burner offers an ideal method of study since the
flame floats in air out of contact with any surfaces. These studies are now
underway.
Problem 1R2 - The Source of Ionization in Flames. The purpose of the present
research is to investigate the theoretical reasonableness of certain ionized-
product reactions taking place under flame conditions, and then perhaps to
account for part of the abnormal ionization observed in reaction zones. A
typical such reaction would be CO*(iit +0 CO2++ e- (where * denotes an
excited state), where CO*(AIII) +0 CO2+ 313 kcal/mole and the ionization
potential of CO2 is 318 kcal/mole.
The first step in a problem of this sort is to calculate the pertinent
potential-energy surfaces for a given reaction. A mass point sliding about
on this surface can then be made to represent the analogous motion of the
reacting system as a function of the nuclear coordinates. Finally, if the
energy surface of the ionized product (say CO2+) crosses or approaches that
of the activated complex, the probability of a transition to the ionized.
state may be calculated quantum mechanically and the result used in a theory
of reaction rates.
During the present report period, work has continued on the above re-
action with emphasis on the linear symmetrical configurations of CO2 and
CO2t, the outer regions of the surfaces having been completed. Many of the
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Experiment, Ino.
Combustion Phenomena
difficult three-center integrals for the inner regions have already been
computed. A modified Roothaan (5) self-consistent field procedure (molecular
orbital theory) is being employed and the complex iterations being performed
on the NORC calculator at Dahlgren, Virginia.
In contrast to the work of Mulligan (6) at Catholic University on the
ground state of CO2 at its equilibrium configuration, localized molecular
orbitals are being used to describe certain of the electrons. Although
Mtlligan's method is more general in form than the present one and does tot
predict localization, reasons for this have been discovered and corrections
made. The result is a reduction in the number of variational parameters
from fourteen to two (not counting screening constants), an enormous mathe-
matical simplification in view of the exceedingly complicated iterative pro-
cedures involved. Recent rough calculations have resulted in orbital ioniza-
tion potentials that are not far different from those of Mtlligan, whenever
comparisons can be made.
Furthermore, there are certain preliminary restrictions on several of
the screening parameters which are inherent in the present setup and not in
the nonlocalized one. This further simplifies the procedure. It is the
opinion of this author (W. E. M.) that the net result will be a considerable
improvement over-all previous work on this molecule. It might be mentioned
here that the ideas involved are not restricted to CO21 and if the method
works, general molecular orbital theory will be considerably simplified
mathematically for complex molecules.
-
110
;,-..V" . ? ? ,
?
?V,
41.
Experiment, Inc. Combustion Phenomena
During the remainder of this contract period, it is hoped that the in-
vestigation of the CO*+ 0 reaction will be completed, with a publication in
the near future on the ground-state energy of CO2 using the aforementioned
modifications.
Preliminary work has also begun on several of the other more promising
reactions.
References
(1) A. G. White, J. Chem. Soc., 127, 672 (1925).
(2) A. C. Egerton and S. K. Thabet, Proc. Roy. Soc. (London), A2111 445-471
(1952).
(3) H. F. Coward and G. W. Jones, U. S. Bur. Mines Bull. No. 279 (Revised),
1938.
(4) G. N. Badami and A. C. Egerton, Proc. Roy. Soc. (London), A2281 297-322
(1955).
(5) C. C. J. Roothaan, Revs. Mod. Phys., a, 69-89 (1951).
(6) J. F. Mulligan, J. Chem. Phys., 22, 347-362 (1951).
111
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?
M. I. T.
Combustion Phenomena
HIGH OUTPUT COMBUSTION
Massachusetts Institute of Technology - Phase 1
Hoyt C. Hottel and Glenn C. Williams, Phase Leaders
Olav B. Blichner, Noble M. Nerheim, and W. Paul Jensen
Introduction
The studies made under this program pertain to burning rates and mecha-
nisms in well-stirred reactors. In the most recent experimental work the, in-
fluence of flow characteristics and mixing on overall reactor performance was
systematically studied. The object of the present phase of the work is to de-
termine chemical kinetic parameters for several fuels, from measurements of
temperature, and composition in a new small model of the, stirred reactor.
Discussion
Problem 1R1 - Burning Rates in Well-Mixed Reactors. During nine months as a
Visiting Fellow at MIT, Mr. Olav Blichner condficted an experimental investi-
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.;;
Ccenbuation Phenomena
gation of the fluid dynamic features of stirred-reactor performance. His re-
duction of the data was unavoidably deferred, so that the results of the work
have only recently become available here and only in graphical and tabular
form. In the absence of a written appraisal of the results by Blichner, it
seems advisable in this report simply to indicate obvious features of the
results, with the expectation that a SQUID technical report on the subject
can be written fairly soon.
In Blichner's work there were three primary objectives: (a) to determine
by tests with a readily-controlled feed mixture the effect on blowout flow
rates of the size of feed holes in the reactant-feed sphere; (b) to assess
the influence on mixing conditions (and thus on blowout) which might result
from variations in pressure drop, as required to maintain flow rates; and (c)
to determine as clearly as possible the value of "n", the pressure exponent
in the loading parameter NA/VP" (where NA indicates moles of air per second,
V the reactor volume in liters and P the pressure in atmospheres.) An addi-
tional objective, that of visual study of flow patterns in a stirred reactor,
was added late in the program and partially realized by brief tests with a
vycor-walled cylindrical reactor.
In the main experimental work, a spherical reactor of 4-inch i.d.,
7 1/2-inch o.d., and having 80 exhaust holes was made. The reactor was fed
by either of two 3/4-inch o.d. inner spheres, one with 24 holes each 0.055
inches in diameter, the other with 80 holes each 0.030 inches in diameter.
Earlier work (1) had indicated that, at lean blowout, higher loading was pos-
114
krt
'7)*
M. I . T .
Combustion Phenomena
sible in the 80-hole feed source when the holes were 0.030" diameter than
when they were 0.055. This was presumably because of the faster mixing made
possible thereby, - a conclusion at variance with earlier literature (2)
claiming that the stirred reactor operates under conditions in which mixing
has been eliminated as a factor. In the present work (and not in the earlier
work) the total feed hole area was kept constant so that the pressure drop
required for a given mass flow rate was the same through either 80 holes or
24. The fuel used was commercial propane, approximately 96% pure.
The present results have been plotted as NA/VP1.8
vs. generalized fuel
fraction, F, and equivalence ratio, o, for convenience in comparing with the
results of Longwell and Weiss (2) and the MIT work (1). If half a dozen wild
points (out of nearly 200) can be ignored, it appears that (a) from a lean 9
of 0.4 to the stoichiometric value the band covered by Blichner's data for a
four-fold range of mass flow rates and for both feed spheres nicely spans the
Longwell and Weiss data obtained with isooctane, and- lies below Baker's data
at o 0.65 but decidedly above these at stoichiometric. On the rich side
Blichner's blowout points are richer than those of both previous investiga-
tions. Blichner's lean (but not .his rich) data cover as wide a range on the
loading parameter scale as do those of Longwell and Weiss.
Considering the effect of feed hole size on allowable loading the follow-
ing results are clear: (a) At NA/VP1.8 values between about 1.0 and 3.0,
there is no distinction in blowout points due to differences in feed spheres,'
(b) At higher loading rates and o's up to about 0.7, the blowout points are
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M.I.T. Combustion Phenomena
leaner for the 80-hole feed sphere. These results are most clearly evident
in a series of plots showing results with nearly constant mass flow rates,
and the maximum difference is somewhat less than 0.1 unit on the 9 scale.
(c) A transition occurs at 0.749