聚心火焰与诱导激波相互作用及爆燃转爆轰过程

Interaction of implosion flame and induced shock wave and DDT

关键词:  爆轰  聚心火焰+  激波  数值仿真

Key words:  Detonation  Implosion flame+  Shock wave  Numerical simulation

摘要:

基于带化学反应的二维轴对称Eu ler方程,利用带限制函数的波传播算法,在两端均敞开和一端封闭一端敞开的两种边界情况下,对圆柱型燃烧室中的氢气-空气预混气的聚心燃烧进行了数值模拟,探讨了聚心火焰引发爆轰过程中的波系结构以及火焰的变形。数值结果表明,在两端均敞开的情况下,燃烧诱导的激波在轴心、火焰和壁面之间来回反射,使火焰失稳,加速了火焰的燃烧,但没有转变成爆轰。而在一端封闭的情况下,封闭端反射产生的激波,不断穿越火焰,使火焰严重失稳,加剧了燃烧速度,最终导致爆轰的形成。稳定爆轰阵面的参数与CJ理论计算的结果进行了对比,两者符合的较好。同时,火焰在与激波的作用过程中,形状扭曲变形,对于两端敞开的情况呈对称的扁平头部蘑菇云,而对于一端封闭的情况,则呈封闭端小敞口端大的扁平头部蘑菇云。

Abstract:

Based on two-dimensional axisymmetric Euler equations,coupled with chemical reactions,the phenomena of implosion combustion were numerically studied by using wave propagation algorithm with Superbee limiter in the cylindrical combustor for two types of boundaries.The wave structure and flame distortion in DDT were discussed according to the calculated results.In the cylindrical combustor with two open ends the simulations show that shock induced by combustion reflecting back and forth from walls and the axis of the combustor gives rise to multiple shock-flame interactions.The shock-flame interactions,through the Richtmyer-Meshkov instability,enhance the flame combustion, but fail to transit to detonation.In the case of one closed and another open end the calculated results show that reflected waves from closed end frequently penetrate the flame,leading to continuous flame excitation and forms turbulence. Finally,DDT occurs.The calculated parameters of steady detonation wave front are compared with those of CJ theory,and the good agreement can be obtained.Simultaneously,repeated shock-flame interactions cause instability and distortion of the flame,and then form the shape of symmetrical collapsing flame front in the first boundary and asymmetrical collapsing flame front in the latter boundary.