脉冲燃烧风洞中空气节流对煤油燃料超燃冲压发动机火焰稳定影响研究

Study on Flame Stabilization in a Kerosene Fueled Scramjet Combustor with Air Throttling in aPulse Combustion Wind Tunnel

关键词:  超燃冲压发动机  空气节流  煤油  火焰稳定

Key words:  Scramjet  Air throttling  Kerosene  Flame stabilization

摘要:

采用试验与数值模拟方法研究了空气节流对煤油燃料超燃冲压发动机火焰稳定的影响。发动机入口气流总温、总压和马赫数分别为1100K，1.0MPa和2.0。空气节流位置距离发动机入口625mm，空气节流流量为入口发动机空气流量的27.2%。多种非接触光学测量手段被应用于超燃冲压发动机燃烧流场结构和火焰传播规律的诊断，包括纹影、阴影、差分干涉、自发光照相和OH-PLIF。首先考察了有、无空气节流时超燃冲压发动机冷流流场的结构，结果显示:在实施空气节流后，流场内产生了激波串结构。激波串促使流场的静温和静压升高，马赫数降低。同时激波串与边界层相互作用，导致了边界层分离，促进了燃料与空气的高效混合，实现了煤油的可靠点火。其次考察了先锋氢气燃烧流场的火焰传播规律与稳定形态，结果表明:当先锋氢气当量比为0.3时，燃烧流场振荡；当先锋氢气当量比为0.1时，燃烧流场稳定。最后研究了空气节流对煤油燃料超燃冲压发动机火焰稳定的影响，结果表明:不实施空气节流时，液态室温煤油吹熄了先锋火焰，煤油点火失败；实施空气节流后，煤油成功点火，当先锋氢气和空气节流撤除后，煤油仍然保持稳定的燃烧。

Abstract:

In order to investigate the effects of air throttling on flame stabilization in a kerosene fueled scramjet combustor， numerical and experimental results were showed in the present paper. Stagnation conditions were 1100K and 1.0MPa and the Mach number at the isolator entrance was 2.0. The location of air throttling was 625mm downstream the combustor entrance， and the flux ratio (the ratio of air throttling flux rate to inflow flux rate) was 27.2% . Various measurements included schlieren， shadow， differential interferometry， flame emission and OH-PLIF were made during the experiments in an attempt to better understand the combustion flow structure and flame development. The flow structure of non-reacting flow with and without air throttling was investigated firstly， the results showed a shock train was generated by the throttling air in the combustor. The resultant increased in the temperature and pressure of the flow in the combustor， along with the decrease in the flow velocity， lead to smooth and reliable ignition. The flame development and stabilization of pilot hydrogen was studied secondly， when the ER of pilot hydrogen was 0.3， the pilot flame oscillated with the combustion flow; when the ER of pilot hydrogen was 0.1， the combustion flow was stable. Finally the effects of air throttling on flame stabilization were investigated， the pilot flame in the combustor without air throttling was blown off by the room temperature liquid kerosene. But the kerosene was ignited successfully by the pilot hydrogen with the aid of air throttling， and even when the throttling air and pilot hydrogen were removed， the flame was still stable.