1、RESEARCH MEMORANDUM PRESSURE LIMITS OF FLAMl3 PROPAGATION OF PURE HYDROCARBON-AIR MIXTURES AT REDUCED PRESSURE By Adolph E. Spakowski Lewis Flight Propulsion Laboratory C leveland, Ohio NATIONAL ADVISORY COMMITTEE FOR AERONAUTICS Provided by IHSNot for ResaleNo reproduction or networking permitted w
2、ithout license from IHS-,-,-1x NACA RM E52H15 i. RESEARCH ME“ PRESSURE LIMITS aF FLAME PROPAGATION OF PURF, HYDROCARBON-AIR MEEUlBS AT mucm mssms By Adolph E. Spakowski SUMMARY The flammability however, the apparatus and the conditions of the experiments are so-varied that correlations are extremely
3、 difficult. Coward and Jones compiled the.greater part of these data into a single N publication (refere.= 7) . . An attempt was made at this laboratory to select an apparatus and a set of conditio percent by volume Ra f lamuability range, percent-by volume W molecular weight Subscrip-ks : e experim
4、ental - Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-NACA RM E52EU5 Apparatus 3 N m cn 4 In this investigation the tube method of determining pressure- f-bility limits was selected. The specific agparatus employed, a modification of that used in r
5、eference 4, is illustrated in ffgure 1. The fuel metering, mixing, and storing apparatus consisted of a 45-liter galvanized-steel storage tank with sealed stirrer A, fuel capsule B, air inlet H, and precision mmeter C. These components were .mounted within a glass-walled tank containing ethylene gly
6、col, which served as a constant-temperature bath. The bath temperature was thermostatically controlled at preset temgeratures from 50 to llOo C - +0.5O C. The test section consisted of a closed glass tube 1.85 inches inside diameter and 48 inches long, joined by a spherical glass joint to the igniti
7、on section. The flasre t for the three others, from NACA . L .i! Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-NACA RM E52H3.5 5 . I N 4 investigations. The average change of the lean limit, expressed as volume percent fuel in the mixture, for the
8、temperature range involved (25 - 80 C) was less than 0.001 percent per OC. The average change of the rich limit, expressed as volume percent fuel in the mixture, over the same merature rapge was 0.004 percent per OC. These tenperatwe corrections were applied to the data for the ensuing discussions.
9、The tenperatwe of the fuel-air mixture in many cases was different from that of the flame ttibe, which necessitated an investigation of the time required for the gas to assume the flame-tuke temperature. For the merature differences involved, it was found that the gas required a maximum of several s
10、econds to assume the flame-tube temperature. When the lean limit, expressed as volume percent of fuel in the mixture, is plotted against the nuniber of cazbon atoms in the molecule, it decreases quite regularly as the nWer of carbon atoms increases . (fig. 3). The precedFng relation holds true for t
11、he n-a-es and the - n-alkenes. The curves at the top of figure 3 show thz effect of carbon content on the rich lFmft. Here again the limit decreases regularly as the nwIiber of carbon atoms increases. Since the rich flaamnability is a decrease of flammability range aa carbon content increases. 5. li
12、mit is decreasing more rapidly than the lean limit, the over-all effect - The flammability 1-t of the fuel in the mixture, expressed now as the percent stichiometricis plotted against the moleculm weight in figure 4. For the n-alkanes the lean limit increases slightly to limit increases to n-hexene
13、aqd Then decreases to n-decene. The rich limit for the n-arn-nes increases very rapidly from methane to n-heptane and then decreases sharply to n-decane. hitting ethylene, the-first meniber of the series, the n-aEene rich limit increases from propylene to n-hexene, then levels oFf through n-decene.
14、From the curves presented in zhis figure it is seen that the moiecular yeight affects the rich limit to a larger exbent than it affects the lean 1-t. - n-pentane and then zecreases to n-decane; for the n-alkenes the lean The flanrmability rasge, that is the rich limit minus the lean limit, expressed
15、 as volume percent fuel in the mixture, is plotted against the molecular weight in figure 5. All the hydrocarbons studied, plus those of reference 4, are included in this plot. The two coounds that deviate considerably are methane and ethylene. Also included in the plot are five gasoline samples. Be
16、cause of the fair degree of correla- tion sham in figure 5 between the flammbility range and the molecular weight, an expression approxFnustely relating the two properties may be written as follows: Ra = aW b Provided by IHSNot for ResaleNo reproduction or networking permitted without license from I
17、HS-,-,-6 NACA RM E52H15 The constants in equation (1) were evaluated, and the resulting equation R,143w -0 - 70 w respectively; and then decreased to ;-decane Gd g?decene, respectively. The rich limit for n-albanes increased rapidly tu n-heptane and then decreased to :-decane. For the n-alkenes, the
18、 rich lhd-t increased.rapidly to n-hexene and then remained-substantially constant through n-decene. - - 4. The flarrrmabflity range, when expressed as volm percent fuel in the mixture, was found to correlate with the molecular weight raised to the -0.70 power. This relation was evaluated for 8Ll of
19、 the hydrocarbons studied and for several fuels with good agreement. 5. The rich limit was found tu correlate with the lean limit raised to the 0.56 power. The predicted values for the rich limit from this relation agreed well with those experimentally obtained. 6. The correlation between the lean l
20、imit and the net molar heat of combustion was found to hold for the n-alkane and n-alkene series through the ten hydrocarbon members. It was Zso sham thgt the heat of cmbus- tion of the lean limit mixtures was substantially a constant. Lewis Flight Propulsim Laboratory National Advisory Committee fo
21、r Aeronautics CleVehZldJ Ohio 1. Dugger, Goran L. : Effect of InitiaLMixture Temgerature on Flame Speed of Methane-Air, Propajle-Air, and Ethylene-Air Mixtures. NACA Rep. 1061, 1952. (Supersedes NACA TN 2374-r) 2. Dugger , Gordon L., and Grabb, Dorothy D. : Flame Speeds of 2,2,4- Trimethylpentme-Oxy
22、gen-Nitrogen Mixtures. NMA TN 2680, 1952. 3. Metzler, Allen J. : Minimum Ignition Energies of Six Pure Bydrocarbon Fuels of the C2 and c6 Series. NACARM E52F27, 1952. 4. DiPiazza, James T. : Limits of Flammability of Pure Hydrocarbon-Air Mixtures at Reduced Pressures and Room Temperature. NACA RM E5
23、1C28, 1951. 5. Spakowski, Adolph E., and Belles, Frank E. : Variation of Pressure Limits of Flame h-opagation with Tube Diameter for Various Isoocfpe- Oxygen-Nitrogen Mfxtures. NEA RM E52M8, 1952. Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,- 6. B
24、elles, Frank E., and Simon, Dorothy M. : Vmiation of the Pressure Limits of Flame Propagation with Tube Diameter for Propane-Air Mix- tures. NACA RM E51J09, 1951. 7. Coward, H F . , and Jones, G. W. : Limits of Flammability of Gases ad Vapors. Bull. 503, Biu:. Mines, -52. 8. Egerton, Alfred, and Pow
25、ling, J. : The Limits of Flame Propagation at Atmospheric Pressure. I. The influence of “Promoters.“ Bot. Roy. SOC. (London), ser. A, vol. 193, May 27, 1948, pp. 172-190. 9. Burgess, Maurice John, and Wheeler, Richard Vernon: The Lower Limit of inflammation of Mixtures of Paraffin mocarbons with Air
26、. Jour. Chem. SOC. Trass. (London), vol. XCIX, pt. 11, 1911, pp. 2013-2030. 10. White, Albert Greville: Limits for the Propagation of Flame in Inflammable Gas-Air Mixtures. Pt. I. Mixtures of Air and One Gas at the Ordinary Temperature and Pressure. Jour. Chem. SOC. Trans. (London), vol. Cm, pt. 11,
27、 1924, pp. 2387-2396. . Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-10 Average for 31 hydrocarbonsa Gasoline Ab Gasoline b Gasoline C Gasoline D Gasoline E Average for 5 gasolines Actual deviation (Fuel, percent by volume 1 Deviation (percent) 0.
28、6 16 -0.1 7 0.4 -2 -5 -0.15 -2 -8 0.19 3.4 &Except ethylene and methane. bReference 7, temperature effect unknown. TABLE I1 - EVALUA!I?ION OF THE ExpaESSION R = 7.1 Lo 56 Average for 32 hydrocarbons* Gasoline b Gasoline b Gasoline C Gasoline-D Gasoline. E Average for 5 gasoline6 Le 0.5 1.4 1.0 -1.1
29、0.1 0.3 0.78 -%xcept ethylene. “ 0.0 0.5 -0.3 0.1 - 0.3 0.24 6.0 19.7 20.8 -14 -9 - 1.5 4.8 12.3 Ld “ 0.0 9.4 -4.2 1.5 4.6 3.9 “ .- . bReference 7, temperature effect unknown. Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-. . . . . . . , . . . . .
30、. . . . . . . . . . 1 . . . . . . . . “. . . I a L99Z I Storage tank Fuel capsule Precision nanometer Flame tube Pressure gage Ignition coil Resistance-wound furnace Dried& inlet 1.1 variac - - 110 v - Watt meter Fieme 1- - Aaparatue for determining fhmabiuty mt. . . . P F . . . . . . . Provided by
31、IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-0 80 160 2rbo 320 4 Fuel, percent atoichlcrmetric (a) =-Pentane and air. Flsme-t*e temperature, 28O C- Figufe 2- - Pressure-f-bility limits in closed flame tube. 0 c Provided by IHSNot for ResaleNo reproduction or
32、networking permitted without license from IHS-,-,-aCA RM E52Hl.5 Q) N u1 4 Fuel, gercent stoichiometric (b) g-HeXene and air. Flame-tube teqperature, SOo C. Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-14 NACA RM E52El5 Fuel, percent stoichiometri
33、c (c) &-Heptane and sirl I FLanae-tee t-rgtv-e, 50 C I. Figure 2. - Continued. Pressure-f-bbiUty lindts in closed flame tube. . . . “. 1-11 1 Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-NACA RM E52Bl5 15 80 160 240 320 400 Fuel, percent etoichiom
34、etric (a) ctane and air. Flame-tube temperature, Soo C. Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-16 NACA HM E52Hl.5 Fuel, percent etolchimetric (e) E-lonane and air. Fume-tube temperature, 80 C. Provided by IHSNot for ResaleNo reproduction or
35、networking permitted without license from IHS-,-,-360 320 280 240 160 40 Fuel, percent stoichiometric (f) E-Decane and ab. Flame-tube tenperatme, 8oo C. Figure 2. - Continued. Pressure-flammablllty limits in cloaed flame tube. 17 Provided by IHSNot for ResaleNo reproduction or networking permitted w
36、ithout license from IHS-,-,-4 18 NACA RM E52Hl.5 0 160 240 . 320 400 Fuel, percent etoichicrmetric (g) g-Hexene and air. Fb-tube temperature, 50 C. Figure 2. - Continued. Preesure-fLslrPoabllty limits in &sed flame tribe. Provided by IHSNot for ResaleNo reproduction or networking permitted without l
37、icense from IHS-,-,-I IWCA RM E52El5 0 00 160 240 320 4 Fuel, percent stoichimetric . (h) l-0ctene and alr. Flame-tube temperature, 80u C. Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-20 NACA RM E52Hl5 Fuel, percent stoichiometric (i) 1-Decene and
38、 alr. Flame-tube temgerature, 8 C. Figure 2. - Continued. Preeeure-flammbility UlaitS in cloaed flame tribe. Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-NACA RM E52Hl5 21 . Fuel, percent stoichla+ric (J) Benzene and air. Flame-tube temperature, S
39、Oa C. Figure 2. - Continued. heesure-flammabil.ity Limit6 in closed flame tube. Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-22 NACA 3RM E52Hl.S 360 320 280 240 120 40 0 3 “97 00 160 240 , 320 44 Fuel, percent atoichiametric (k) Toluene and ah-. F
40、lame-tube tempsatme, 50 C. Figure 2. - Continued. Pressure-flanrmrabilty limits in closed flame tube. . Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-NACA RM E52ECL5 23 3 Fuel, percent stoichiometric (1) E-Xylene and air. Flame-tube temperature, 80
41、 C. Figure 2. - Continued. Pressure-flannnabilitybility llmits in closed flame tube. Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-24 360 320 280 240 120 0 NACA RM E5ZEl5 80 160 z4.0 320 Fuel, percent 6tDlchiometric “ c . Provided by IHSNot for Res
42、aleNo reproduction or networking permitted without license from IHS-,-,-4x i eo 0 cn 4 I . 25 80 160 240 320 4m 480 Fuel, percent stoichiometric Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-26 NACA RM E52Hl.5 Fuel, percent stoichimetric ( 0) Methy
43、lcyclohexane and air. -tube temperature, 50 C. Xigure 2. - Continued. Preateaure-flnmmRhility llmita in cloaed flame tube. . . .m. N Y Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-27 . . . Provided by IHSNot for ResaleNo reproduction or networking
44、 permitted without license from IHS-,-,-2% NACA RM E5ZKI.S Fuel, percent stolchiametric (q) Di-isopropgl and air. FLame-tme temperature, 500 C. FQurc 2. - Continued. Preeeure-flannuabillty UmLts in clceed flame tube. Provided by IHSNot for ResaleNo reproduction or networking permitted without licens
45、e from IHS-,-,-NACA RM E52H15 29 N 0, 8 1 * U 0 160 240 320 I P I Fuel, percent stoichiometric (r) 2,2,4-R.imethyLpentane anB air. Flame-tube teqperature, 500 C. Figure 2. - Concluded. Pressure-flammability limits in claaed flame tube. Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-
