Mcdonald, Glen E

Schalla, Rose L

English

NASA Technical Reports Server

RM E54E03 
NACA 
RESEARCH MEMORANDUM 
EFFECT OF HIGH PRESSURE ON SMOKING TENDENCY OF 
DIFFUSION FLAMES

By Glen E. McDonald and Rose L. Schalla 
Lewis Flight Propulsion Laboratory
Cleveland, Ohio 
ENGINEERING DEPT. LIBRARY 
CHANCE VOUCUT AIRCRAFT 
INCORPORATED 
DALLAS, TEXAS 
NATIONAL ADVISORY COMMITTEE 
FOR AERONAUTICS 
WASHINGTON 
June 28, 1954
https://ntrs.nasa.gov/search.jsp?R=19930088295 2020-06-17T07:43:22+00:00Z
NACA RM E54E03
NATIONAL ADVISORY COIVIIVII'PI'EE FOR AERONAUTICS 
RESEARCH MEMORANDUM 
EFFECT OF HIGH PRESSURE ON SMOKING TENDENCY OF DIFFUSION FLAMES

By Glen E. McDonald and Rose L. Schalla 
SUMMARY 
The variation in smoking tendency of a diffusion flame was measured 
over a pressure range of 4 to 20 atmospheres (abs) for the two fuel types 
ethane and ethylene. The fuels were burned as diffusion flames inside 
a pressure vessel equipped with windows for observation of the flame. 
It was found that the changes in flame height, which measures the rela-
tive amount of fuel that can be burned without producing smoke, vary 
inversely with the pressure.
INTRODUCTION 
A previous investigation of the relation between smoking tendency 
of a diffusion flame and variations in pressure has been reported (ref. 
1). In that work the relative smoking tendency was determined for sev-
eral pure fuels and blends of fuels from pressures of 1/2 to 12 atmos-
pheres (abs). The results indicate that over this pressure range the 
maximum smoke-free fuel flow is inversely proportional to the pressure. 
The purpose of the present study was to obtain a more complete relation 
between smoking tendency andpiessure by extending the pressure range 
to 20 atmospheres. 
At the NACA Lewis laboratory two gaseous fuels, ethane. and ethylene, 
were investigated over a pressure range of approxihately 4 to 20 atmos-
pheres. Smoke was defined as the release of unburned carbon from the 
flame. Smoking tendencies were determined by burning the fuels as dif-
fusion flames in a pressure tank and measuring the maximum .elative flame 
height at which the fuels could be burned without producing ioke. 
APPARATUS AND PROCEDURE 
The apparatus used in the investigation is shown in figure 1. The 
pressure tank is similar to the tank used previously (ref. 1) but has 
been designed for higher pressure. The tank is 7 inches in diameter and 
17 inches high. Lucite windows 2 inches in diameter and 2 inches thick 
ENGINEERING DEPT. LIBRARY 
CHANCE VOUGHT AIRCRAFT
INCORPORATED 
DALLAS, TEXAS
	 JUL
. i54
2	 NACA RN E54E03 
served as observation ports. Air was supplied near the bottom of the 
tank from a cylinder of compressed air. Combustion products were re-
moved through a valve in the top of the tank. Air flow during a run was 
adjusted to give the flame an adequate supply of fresh air. It has been 
determined that air flow within the ranges used had no effect on the 
smoking tendency (ref. i). 
The fuels, under high pressure, were supplied to the pressure tank 
from cylinders. The flow of fuel was adjusted by a valve in the line 
between the fuel cylinder and the pressure tank. The fuels were burned 
from a 2-millimeter-inside-diameter tube with a 0.5-millimeter wall. 
For measurement at a given pressure, the rate of fuel flow was adjusted 
until the flame was at its incipient smoking point. The height of the 
flame above the base of the burner was then measured with a cathetometer. 
The ethane used was Matheson Co., Inc. c.p. grade, and the ethylene 
was Ohio Chemical & Mfg. Co. c.p. grade. 
Variation in the size of the burner may change the amount of fuel 
which can be burned smoke-free. Therefore, the data obtained in this 
investigation show only the relative variations in smoking tendency at 
various pressures.
RESULTS AND DISCUSSION 
In figure 2, the maximum flame height at which the fuels could be 
burned without smoking is plotted against pressure. In table I and fig-
ure 2, it may be observed that the flame height at the smoking point de-
creases consistently up to the highest pressure studied. 
It was previously found (ref. i) that below the smoking point, an 
increase in pressure did not change the flame height fora constant 
mass fuel flow. This confirmed the observations reported in other lit-
erature (ref. 2). When the fuel flow to a flame is increased until the 
flame reaches the smoking point, there is a gradual change in the flame 
height. However, at the smoking point there is an abrupt change in the 
flame height. Consequently, measurements of the flame height very close 
to the smoking point may have a lower precision than measurements of the 
fuel flow which were reported previously (ref. 1). However, because of 
the difficulties in calibrating flow meters for use at these pressures, 
flame heights. were measured in these experiments. The precision of 
measurements may be observed in figure 2 from the measurement of the 
smoking tendency at nearly equal pressures,. 
The amount of fuel burned is directly related to the flame height. 
Therefore, the amount of fuel which can be burned smoke-free decreases 
progressively up to the highest pressure studied of 20 atmospheres. The 
results shown in table I and the general shape of the curve in figure 2
NACA RM. E54E03	 3 
indicate that the relation between smoking tendency and pressure which 
was observed previously (ref. i) is also present up to pressures of 
20 atmospheres. 
In previous work (ref. i), a plot of smoke-free fuel flow against 
reciprocal pressure gave a straight line for each fuel. It was con-
cluded that the smoke-free fuel flow could be correlated with the change 
in the diffusion coefficient since the diffusion coefficient is inversely 
proportional to pressure. In figure 3, flame height is plotted against 
reciprocal pressure up to 20 atmospheres for the fuels investigated. 
The straight lines indicate that the change in the fuel flow at the 
smoking point is inversely proportional to the pressure. 
As the fuels burned in atmospheres of higher pressure, there was 
an increasing tendency for carbon to deposit on the lip of the burner. 
The formation was hard and coherent and when once started, it increased 
rapidly. During-its growth, the carbon cone was maintained at a red 
heat by the flame. The tendency for the hard carbon to deposit on the 
burner occurred only when the flame was above the smoking point. 
SUMMARY OF RESULTS 
An investigation of the smoke-forming tendency of hydrocarbon dif-
fusion flames over a pressure range of 4 to 20 atmospheres gave the 
following results: 
1. The change in the amount of fuel, as measured by the flame 
height, which could be burned smoke-free was inversely proportional to 
pressure. 
2. The same relative variation with pressure was observed for the 
two fuel types ethane and ethylene. 
3. At higher pressure there was an increasing tendency for hard 
carbon deposits to form on the burner. 
Lewis Flight Propulsion Laboratory 
National Advisory Committee for Aeronautics 
Cleveland, Ohio, May 3, 1954 
REFERENCES 
1. Schalla, Rose L., and McDonald, Glen E.: Effect of Pressure on the 
Smoking Tendency of Diffusion Flames. NACA RM E53E05, 1953. 
2. Parker, W. G., and Wolfhard, H. G.: Carbon Formation in Flames, 
Pt. III. Jour. Chem. Soc. (London), Aug. 1950, pp. 2038-2044; 
discussion, pp. 2045-2049.
NACA RM E54E03 
TABLE I. - VARIATION OF FLAME HEIGHT AT SMOKING POINT

WITH PRESSURE 
Ethane Ethylene 
Pressure, Flame Reciprocal Pressure, Flame Reciprocal 
atm abs height, pressure, atm abs height, pressure, 
cm -1 
atm cm -1 atm 
6.4 3.20 0.156 4.4 1.93 ,0.227 
6.4 3.15 .156 
8.5 2.84 .118 7.8 1.09 .128 
11.0 2.03 .091 
11.9 2.10 .084 11.9 .79 .084 
14.6 1.74 .068 15.6 .67 .064 
14.6 1.67 .068 
15.6 1.79 .064 18.7 .53 .053 
18.0 1.48 .055 
21.4 1.71 .047 20.7 .48 .048 
22.2 1.45 .045
Cover 
'ressure gage 
ucite window 
NACA RN E54E03
	
5 
-	 A4-..	 -,,.-..1-
CD-3641] 
Figure 1. - Apparatus for determining smoking tendency at high pressure.
63.6 
3.2 
2.8 
2.4 
1.6 
1.2 
.8
NACA PM E54E03 
- -
 
Hydrocarbon-
Ethylene 
Ethane 
Iii±\;IiIIIIi 
- 
-T - --- - 
---4----IIi1\IIIIIIIi 
- - --- - ---H - 
------'------
-
- 
2.0 
4)
.4 
0	 4	 8	 12	 16	 20	 24
Pressure, atm abs 
Figure 2. - Flame height at smoking point against pressure. 
Flame height proportional to fuel flow.
NACA RN E54E03
	
7 
0 III 0  IIII_IIIIIII 
JCL 
----
----N-
- 
--
.ND---
-- v -- - --a- - 
0	 CL	 C'	 CL) 
N	 C'i
mo 't9t ouri&
CD
CH 
H 
H 
CD 
C'J
0 
4.' 
H 
P4 
0 
0 
	
C3	 ..-I 
CD 
- 
CD 
cD
	
•	 P4 
CD H 
6)
0 
0 
CD 
a, 
C) 
0' 
'!CD
0 
PC 
0
M 
4.' 
	
CD	
03 
	
o	 -p 
40 
CD 
o
r=4 
N, 
0 
0	 (0	 C'3• 
H
rI 
NACA-Langley - 6-28-54 - 350


Effect of high pressure on smoking tendency of diffusion flames

Abstract

Similar works

Full text

Available Versions

NASA Technical Reports Server