Experimental study on ignition process for ethylene high speed jet
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摘要: 为了研究超燃冲压发动机燃烧室流动状态下的富燃燃气点火过程，设计建立了一套用于研究高速乙烯射流在富燃燃气中点火过程的高温同轴射流试验装置。试验研究了伴流当量比1.4和1.6，乙烯射流喷注压力2×105Pa和3×105Pa参数下的点火过程，试验过程中乙烯射流均能实现稳定燃烧。结合高速摄像机和后处理分析点火过程发现：（1）乙烯高速射流在富燃燃气中的点火过程主要分为4个阶段：（a）主流和伴流掺混；（b）主流和空气发生剧烈化学反应；（c）火焰在下游发生局部熄火；（d）火焰达到稳定状态。（2）伴流当量比1.4比伴流当量比1.6更有利于高速流动下的点火。（3）乙烯射流速度的增大会导致不充分燃烧，火焰亮度变弱。Abstract: In order to investigate the ignition process with fuel-rich gas of scramjet combustor, a simplified burner with fuel-rich hot coflow and sonic nozzle jet was designed. Ignition process of sonic ethylene jet issuing into a coflow of hot exhaust products of a rich premixed ethylene/air flat flame was examined using the chemiluminescence. Three cases with the equivalence ratio of coflow varying from 1.4 to 1.6 and the injection pressure varying from 2atm to 3atm were examined. The results indicate that:(1) the ignition process of sonic ethylene jet in fuel-rich gas may be divided into four steps:(a) jet and coflow mixing; (b) strong chemical reactions between jet and surrounding air; (c) occurrence of extinction in the downstream of flame; (d) steady flame; (2) the equivalence ratio of coflow 1.4 was more effective than 1.6 for ignition process; (3) with the increase of jet velocity, flame luminosity is lowered due to incomplete burning in the higher speed steady flame.
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Key words:
- scramjet combustor /
- ethylene /
- high speed jet /
- ignition process /
- high speed camera
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图 2 工况1和2的点火过程
Figure 2. Chemiluminescence images of ignition process for case 1 and case 2
图 3 点火过程中工况1和2总亮度值随时间的变化
Figure 3. Integrated chemiluminescence in observation area of case 1 and case 2
图 4 工况1和3的点火过程
Figure 4. Chemiluminescence images of ignition process for case 1 and case 3
图 5 点火过程中工况1和3总亮度值随时间的变化
Figure 5. Integrated chemiluminescence in observation area of case 1 and case 3
表 1 试验工况
Table 1. Experimental conditions
Case Coflow 
Main
jet
p/105PaMax
main jet
v/(m·s-1)Max
Mach
numberCoflow
u
/(m·s-1)1 1.4 2 345 1.1 1.5 2 1.6 2 345 1.1 1.5 3 1.4 3 439 1.4 1.5 
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表 2 伴流的温度和组分质量分数
Table 2. Temperature and species mass fraction of coflow
Coflow Temperature
T/KH2
/%CO
/%CO2
/%H2O
/%1.4 2254 0.3 10.8 10.3 8.5 1.6 2132 0.5 14.7 7.7 7.9
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