爆震发动机超声速进气道的非定常耦合流场数值研究

采用带化学反应的非定常数值仿真方法,对爆震发动机(PDE)内进气道、燃烧室、尾喷管的耦合流场进行了分析,并着重研究了爆震压力波及其反射波对超声速进气道内流动结构的非定常干扰过程,对比了3种进气道/燃烧室耦合方式下进气道流动特性的差异.结果表明:通过在燃烧室内填充以化学恰当比预混的燃料和氧化剂,数值仿真可获得稳定自持的爆震波.在爆震波压强作用下所产生的结尾波系和反射激波会发生耦合干扰作用,它们在流道内的运动传播影响了结尾波系的前传幅度.通过对比不同进气道/燃烧室耦合方式的流场特征发现:采用突扩式进气道/燃烧室连接段可利用燃烧室头部固壁的阻碍以及其对爆震高压波的反射作用将大部分的压缩气体存储于燃烧室内,进而减弱进气道与燃烧室之间的耦合干扰作用,对提高进气道的工作稳定性有利.另外,内凹式燃烧室头部段的引入还为压缩气体提供了额外的存储空间,故可以进一步缓冲爆震高压,提高进气道的稳定工作裕度.

Numerical investigation on unsteady flow structure in supersonic inlet coupled with pulse detonation engine combustor

The flowfield in a supersonic inlet coupled with a pulse detonation engine(PDE) combustor and nozzle was numerically studied by an unsteady CFD method involving chemical reactions.Emphasis was placed on the flow structure of the supersonic inlet which was unsteadily interfered by the detonation wave and its reflected shock.A comparison of the performances of the three models using different coupled methods was also conducted.Results indicate that by injecting premixed fuel and oxidant into the combustor,stable and self-sustaining detonation wave is successfully generated in the combustion process.Due to the pressure perturbation caused by the detonation wave,a shock system and a reflected shock are generated in the duct.Mutual interference between them is observed,and it is found that their transformation in the duct has affected the oscillatory amplitude of the shock system.By comparing the flow characteristics of the three models with different coupled methods,it is noted that due to the buffering effect of the combustor head wall and the effect brought by the reflected shock,the two models which employ the abrupt diverging conjunction of the inlet and the combustor are able to deposit a majority of the compressed air in the combustor,which in turn significantly weakens the interference between the inlet and the combustor and makes a contribution to the stability of the inlet.Furthermore,the concave combustor head introduced can accommodate an extra volume of the high density compressed air,which results in a further reduction of the detonation-induced pressure,and leads to a larger stability margin of the inlet for the pulse detonation engine.