热射流起爆过程的数值模拟

摘要

An improved uncoupled solver of non-equilibrium flow was adopted to resolve the Euler reacting equations and a chemical H2 /air mixture reaction model with 9 species and 21 equations was employed to conduct the two-dimensional numerical simulation in detonation onset process of vertical hot jets.The convection term was dispersed with fifth-order WENO format and the time integration was iterated with second-order Runge-Kutta scheme.The flow fields in the detonation tube were analyzed in detail when hot jets were injected with different parameters (i.e. incident velocities,incident positions,incident widths and incident angles).And the general rule of the impact of hot jets parameters to the detonation initiation was summarized.Moreover,interaction between shocks and flame during the formation and propagation of “hot spots”was explained,especially the promotion of reflected shocks on the formation of “hot spots”.The investigation reveals that detonation always occurs from the “hot spots”in narrow unburned region which is confined by adjacent flame front and solid wall.Triple point structures emerge during the over-driven transition of “hot spots”to detonation.In order to achieve rapid detonation onset,the hot jets should be injected towards the side wall in high velocity and with a certain angle.%采用改进的化学非平衡流解耦方法处理 Euler 反应流方程，并以 H2／air 9组分21方程模型对竖直喷注的热射流起爆过程进行了二维数值模拟。对流项采用五阶 WENO 离散格式，时间推进采用二阶 Runge－Kutta 方法。详细分析了热射流以不同速度、入射位置、入射宽度和入射倾角喷射时在爆震管内形成的流场，总结了射流参数状态影响起爆的一般规律；解释了激波、火焰的相互作用对“热点”的形成以及转变为爆震的影响，特别是激波反射对“热点”形成的促进作用。结果表明，爆震波通常由火焰面和固壁附近狭长未燃区域中的“热点”产生。“热点”向爆震波发展的过程是过驱爆震阶段，存在三波结构。为了实现快速起爆，应当增大射流入射速度、贴近侧壁并以适当入射角度喷射热射流。