马赫数4下氢气自燃辅助乙烯点火实验研究

Experimental Research on Ethylene Ignition with Hydrogen Self-Ignition Assistant at Mach 4

关键词:  超燃冲压发动机  直连式脉冲燃烧风洞  点火试验  火焰传播 

Key words:  Scramjet  Pulse directly-connected combustion facility  Ignition experiment  Flame propagation

摘要:

为了研究氢气自燃辅助乙烯点火的具体点火参数和点火性能,在直连式脉冲燃烧风洞设备上进行了模拟飞行马赫数4条件下的超燃发动机乙烯点火试验,试验来流的总温935K,总压0.8MPa,隔离段入口马赫数2.1。试验利用不同质量流量的引导氢气自燃辅助点火,成功实现了乙烯燃料的点火和稳定燃烧。通过流场显示和壁面压力测量发现:(1)能够成功点火的引导氢气流量范围为 0.43~12.61g/s,相当于当量比0.005~0.142；(2)0.43g/s流量氢气注入燃烧室后10ms以内被点燃,乙烯燃料注入后经过了约20ms才被点燃,点火的主要位置为凹槽内；(3)6.68g/s的氢气注入燃烧室后20ms才被点燃,乙烯燃料注入后约8ms即被点燃,点火的主要位置为凹槽下游和凹槽出口位置；(4)点火试验中火焰能够在凹槽内和剪切层内向上游逆传；(5)凹槽下游和下壁面的燃烧,是促进凹槽内燃烧、提升燃烧室压力和引起燃烧室压力震荡的主要原因。 

Abstract:

Experiments on scramjet combustor ignition were performed on pulse directly-connected combustion facility in the inflow which simulated the flight Mach 4with the total temperature of 935K, total pressure of 0.8MPa and the inflow Mach number of 2.1to confirm the detailed ignition parameters and performance. Pilot hydrogen at various mass flow rate was employed to achieve ethylene ignition and stable combustion. Results of pressure measurement and high speed imaging indicate that:(1) For reliable ignition the mass flow rate of hydrogen range should be from 0.43g/s to 6.68g/s, the equivalence ratio range is from 0.005to 0.142.(2) Hydrogen at 0.43g/s is self-ignited 10ms after injected, and ethylene is ignited 20ms after injected, the main ignition location is in the cavity. (3) Hydrogen at 6.68g/s is self-ignited 20ms after injected and ethylene is ignited 8ms after injected, the main ignition region is located at the exit and downstream of the cavity. (4) Flame could propagate upstream in the shear layer and in cavity. (5) Combustion downstream the cavity is the main cause of promoting combustion in cavity, improving combustor pressure and pressure oscillation.