热膨胀对窄管道中火焰加速机理的影响

Influence of Thermal Expansion on Flame Acceleration Regime in Narrow Tubes

基于可压缩内维尔-斯托克斯方程,对绝热不可滑移壁面圆管道中从闭口向开口传播的预混合火焰进行直接数值模拟,研究不同火焰加速机理及其转变过程.谢尔金加速机理表明,初始平面火焰在气体热膨胀和壁面摩擦的共同作用下变形进而自加速.对热膨胀系数Θ和无量纲管径Re进行参数研究,分别设置为Θ=3.2~6,Re=10~40.结果表明火焰加速度随热膨胀系数增加而增加,随无量纲管径增加而减小.线性加速机理和指数加速机理之间的临界热膨胀系数Θ_(c)≈3.5且随无量纲管径增加而减小.

In the present study,numerical simulations based on compressible Navier-Stokes equations are per-formed in order to examine the acceleration regime of a premixed flame propagating from a closed end to an open end of a cylindrical tube with non-slip adiabatic walls.The initial planar flame becomes curved and self-accelerates due to the combined effect of the thermal expansion of burnt gas and wall friction,known as Shelkin acceleration.The main parameters are the thermal expansion coefficientΘand the dimensionless tube radius Re,withΘset as 3.2—6 and Re as 10—40,respectively.It is found that the flame acceleration rate increases withΘand decreases with Re.The critical thermal expansion coefficientΘ_(c),separating the linear and exponential acceleration regimes,is around 3.5,which decreases with the increase of Re.