Relative velocities of the flame in a carbon monoxide - air mixture containing either added heavy water or light water were measured in a glass tube. Throughout the range of carbon monoxide - air composition, the flame containing added light water had a faster speed than the flame containing heavy water

Mcdonald, Glen E

English

NASA Technical Reports Server

RM ESOCl( 
RESEARCH MEMORANDUM 
NEASURENIENT OF UNIFORM FLAME MOVEMENT IN CARBON MONOXIDE 
AIR MIXTURES CONTAINING EITHER ADDED D20 OR Hz0 
v By Glen E. McDonald 
Lewis Flight Propulsion Laboratow 
Cleveland, Ohio 
NATIONAL ADVISORY COMMITTEE 
FOR AERONAUTICS 
WASHINGTON 
July 5, 1950 
https://ntrs.nasa.gov/search.jsp?R=19930086164 2020-06-17T12:55:48+00:00Z
. 
. 
c 
mcA IIM EsOClO 
l 
HATIORALADVI9ORYC~ROR AERONAUTICS 
CARBCW MONOXIDE - AIR 
By Glen E. McDonald 
Relative velocities were measured in a glass tube for the 
flame in a carbon monoxide (CO} - air mixture containing either 
added D20 or H20. Differences in temperature, in flame-front area, 
and in movement of the preflame gas occur between the two flames. 
Because these differences were not measured in this investigation, 
only qualitative comparisons can be made between the flame-velocity 
measurements. Throughout the range of CO - sir composition, the 
flame containing added H20 had a faster speed than the flame con- 
taining D20. The flame-speed inurease on addition of increasing 
amounts of H20 to the CO - air mixture was greater than the increase 
produced by addition of increasing amounts of D20. An increase in 
the temperature of the preflsme gas increased the speed of the flame 
that contains H20 more than it increased the speed of the flame that 
contains I&O. A quantitative determination of the relative flame 
velocities of CO - air mixtures containing either added H20 or 
D20 was obtained by Bunsen cone measurement. 
Some investigators (reference 1) have ascribed the fleme 
velocity of a gaseous mixture to the rate of heat transfer from 
the flame front to the unburned gas. Recently the suggestion 
has been made (reference 2) that the diffnsioa of active radicals 
from the flame front may control the flame velocity. It has been 
postulated that active radicals dif'fuse from the flame zone into 
the unburned mixture and there initiate cc&u&ion processes (for 
example, reference 2). The rate of proptigation has been related 
to the hydrogen-atom concentration in the flame zone. The possible 
effect of hydrogen atarns in propagating c&u&ion outweighs the 
effect of other active radicals because the hydrogen atom diffuse6 
many times faster than &ny other radical present in the flame. 
, 
2 HACA RM ESoc10 
If flame velocity could be measured in systems that differ Fd 
the rates of aotive radical diffusion, the effect of radical dif- 
fusion on flsme velocity could be evaluated. This condition may 
be approximated by the use of certain isotopic materials, such as 
deuterium aud hydrogen, that magnify changes in diffusion and 
minimize chsnges in thermal properties. 
In this preli&nary research, which vas conducted at the NAM 
Lewis laboratory -relative flame velocities were measured for car- 
bon monoxide (COj - air mixtures that contained either added heavy 
water (D20) or light water (H20). This report presents the meas- 
urements of flame speed that have been completed to date. These 
two systema differ chiefly in the diffusion coefficient of active 
radicals. The deuterium atom differs from the hydrogen atan in 
having: (1) a much smaller diffusion coefficient; (2) a lower 
thermal equilibrium concentration; and (3) a possible lower rate 
of reaction with the unburned carbon monoxide - air mixture. If 
active radical diffusion influences flame velocity, the velocity 
of the flame that contains hydrogen atoms should be greater than 
the velocity of the flame that contains deuterium atoms because 
the diffusion of hydrogen atoms from the reaction zone into the 
unburned gas is significantly greater than the diffusion of 
deuterium atoms. 
!Vhe use of D20 was approved by the U.S. Atomic Energy 
cclmmission. 
EWERIMENTAL 
The flame tube used in part of these measurements of flame 
velocity is diagrsmmatically shown in figure 1. The 25-millimeter 
inside-diameter Pyrex tube (100 cm long) was fitted with 
8 4-millimeter orifice in one end. Relative rates of flame Prop- 
agatian were measured with this apparatus. The linear rate of 
flame propagation was determined by measuring the time required 
for the flame to move between the two pairs of tungsten electrodes. 
The preparedmixture of CO, air, and water vapor was admitted 
to the evacuated tube, both ends were opened, and the gas was ignited 
by application of a flame to the end opposite the orifice. Photo- 
graphs taken at C4 frames per second showed that the flame front 
areawas constant and that the flamemotionwas unifarm. The Pm 
tube could be replaced with an identiual tube that was externally 
wound with LQicbrome wire to permit preheating of the gas. 
HACA~E5OClO ' 3 
Relative measuraments of flame velocity were also made with a 
Bunsen technique. Shadowgraphs were taken of a projected Bunsen 
cone-that was burningthe desiredmIxture of CO, air, and water 
vapor. The area of the flame front vas determined by measurement 
of the cone photograph. 
The CO used in this investigation was produced by the reaction 
of anhydrous formic acid and concentrated sulfuric acid. Analysis 
showed the carbm monoxide to be at least 99.9 percent pure. The 
stated purity of 99.8 percent for the D20 was ccnfirmed by density 
snd refractive-index measurements. The air used in these measure- 
ments was dried with anhydrous magnesium perchlorate. 
The flame-tube measurements are only qualitative comparisons 
because: (1) The relative areas of the flamea were not measured; 
(2) the pressure and the mc vement of the preflame gases were not 
measured for the different mZxbures; and (3) the effect of the 
tube wall on the temperature and tiee radical ccncentration An 
the flames was not determined. 
The variation of uuiformflamemovement withthe change in 
CO content is shown in figure 2. In these experiments, 1 percent 
by volume of water vapor was added to the CO - air tixture and 
therefore the ratio of water vapor to CO decreases as the CO con- 
centratios increases. With added H20, CO has a faster uniform 
movement of flame than CO with an equal mole fraction of added D20. 
Measurements were also made for a 42-percent CO - 58-percent 
air mixture to which had been added increasing smounts of either 
H20 or D20. The results of these measurements ee plotted in 
figure 3(a). The change in uniform flame movement with a change 
in concentration of added water is less for the flame that con- 
tains D20 thsn for the flame that ccmtsine H20. 
Measurements were made for several temperatures of the pre- 
flame gas on a 42-percent CO - 580percent air mixture that con- 
tained 1 percent of added water vapor. The results are shown in 
figure 3(b). An increase in temperature Increases the speed of 
the flame that contains H20 more than it increases the speed of 
the flame that conkIns D20. 
4 XACA IM E5CClO 
Quantitative determinations of relative flame velocity were 
secured with the Bunsen shadowgraph technique. The velocities of 
a 42-percent CO - S&percent air mixture with 1 percent of added 
water were 8s follows: 
Flame with added D20, cm sec'l . . . . . . . . . . . . . . 32.9 
Flame with added H20, cm sec'l . . . . . . . . . . . . . . 39.5 
Although the dWfusion theory predicts the trends that me rep&ed 
herein, no couclusicms can be drawn as to the application of the 
thermal m diffusion theories until an analysis has been capleted. 
Continued investigation should determine the effect of free radi- 
cal dZfusion on flame speed. 
SUMMARY OF REms 
Measurements of the flame speed of carbon manoxide (CO) - air 
mixtures with added heavy water (D20) and light water (H20) gave 
the following results: 
1. Throughout the range of CO - air ccmpositicn, the flame 
that cmtains Hz0 had a faster speed than the flame that contained 
an equivalent amount of %O. 
2. The flame speed increase upm addition of increasin@ 
amounts of H20 to the CO - air mixt;ure was greater than the 
increase on addition of increasing amounts of D20. 
3. An increase in temperature of the preflame gas increased 
the velocity of uniform movement of the Hz0 flame more than it 
increased the velocity of the flsme that conta¶ned %O. 
4. A quantitative determination of the relative flame veloc- 
ities of CO - air ndxtures that contained either added Hz0 or a0 
was obtalned by Bunsen cone measurement. 
Lewis Flight Propulsion Laboratom, 
National Advisory Ccmmittee for Aeronautics, 
Cleveland, Ohio. 
I'X4cA RM-ESOCIO 5 
1. Hoare, M. F., and Linnett, J. W.: The Mechanism of Flame Prqp- 
agation. Jour. Chem. Phys., vol. 16, no. 8, Aug. 1948, 
pp. 747-749. 
2. Tanford, Charles, and Pease, Robert I.: Equilibrium Atom and 
Free Radical Concentrations in CarbonMonoxide Flames and 
Correlation with Burning Velocities. Jour. Chem. Phys., 
vol. 15, no. 7, July 1947, pp. 431-433. 
A 
B 
Recordbg osclllograph 
Stopcock 
c, C', 
D 
F, F' Ground-glass joints 
4-millimeter orffloe 
E, E' Tungsten electrodes v 
. 
Flgwe 1. - Glass flame tube used in making flame-speed measurements. 
. . . 
SLZT 
c 
1 
NACA R M  E5OC10 7 
80' 
60 
/ 
20 
0 20 40 60 
Carbon monoxide, percent by volume in carbon monoxide - air 
m ixture 
Figure 2. - Flame velocity of carbon monoxide - air m ixtures with 
1 percent of added water vapor. 
8 
t 
NACA RM E5OC IO 
60 
50 
40 
1.0 c 1.5 2.0 
Added water, percent by volume 
(a) Effeot of various amounts of added water vapor* 
ao- 
I I-I/-k-i-I I I7 
60 
25 50 75 100 125 
Temperature, OC 
(b) Effect of varfous preflame temperatures and I percent of 
added water vapor. 
. 
. 
i 
Figure 3. - Flame velocity of 42 percent aarbon monoxide - 58 per- 
cent air mixture. 
NhCh-L.n@ey - 7-5-50 - 100 



Measurement of uniform flame movement in carbon monoxide - air mixtures containing either added D2O or H2O

Abstract

Similar works

Full text

Available Versions

NASA Technical Reports Server