超燃冲压发动机凹腔内补氧的强化点火试验

Enhanced Ignition Experiment with Oxygen Addition into Cavity in Scramjet

关键词:  超燃冲压发动机  燃烧室  点火  火焰传播  凹腔  实验研究 

Key words:  Scramjet  Combustor  Ignition  Flame propagation  Cavity  Experimental research

摘要:

在超燃冲压发动机扩张型燃烧室中,对凹腔内局部补氧的点火强化方法进行了试验研究。采用高速摄影手段研究了不同的补氧方式对凹腔内火焰分布特征和燃烧强度的影响,并针对并联双凹腔燃烧室构型,研究了在单侧凹腔补氧条件下向异侧凹腔的火焰传播过程。试验结果表明,采用凹腔内补氧的方式能调节凹腔内的燃料浓度分布、改善凹腔内的燃烧过程,控制燃烧放热强度；稳态燃烧情况下,观察到凹腔驻留火焰的两种存在特征,分别表现为:由回流区热量反馈机制作用下的凹腔局部驻留火焰和燃烧室全局压力反馈影响下的凹腔剪切层火焰。只有在单侧凹腔燃烧建立了全局压力反馈的条件下才能实现凹腔火焰的异侧传播。 

Abstract:

Enhanced ignition with oxygen addition into cavity in expanding combustor of scramjet was conducted experimentally. The effects of different methods of oxygen addition on the characteristic of flame distribution and intensity of combustion in cavity were investigated with high speed camera. For combustor with double cavities installed in parallel, the process of flame spread from the side of cavity with oxygen addition to the opposite one was observed. Results confirm that the performance of cold-start in combustor can be improved with oxygen addition which can intensify the combustion within cavity due to modulation of the fuel concentration distribution. Once stable combustion obtained, two types of flame existing in cavity can be distinguished, namely trapped flame within cavity due to local feedback of heat release in recirculation zone and flame surrounding the shear layer because of full feedback of pressure response in the whole combustor. For double-cavity-combustor, the first step of fully pressure established circumstance in single cavity is necessary for flame propagation to the other side. 