环形火焰引发爆震的数值研究

Numerical investigations of detonation induced by toroidal flame initiation

关键词:  爆震引发  环形火焰+  热点+  数值模拟

Key words:  Detonation initiation  Toroidal flame~+  Hot spot  Numerical simulation

摘要:

采用改进的适于多组分反应流的波传播算法,对直管道中甲烷-空气预混气的爆震引发过程进行数值研究,考虑了两种不同构型的初始环形火焰对引发爆震的影响。对这两种构型下爆震引发过程中的压力场、温度场、反应放热率以及组分浓度进行了计算,由此探讨了“热点”形成机制及其对爆震引发的作用。结果表明,火焰发展产生的燃烧压缩波在管壁或管轴心发生汇聚、碰撞所形成的复杂波系与火焰相互作用,导致火焰前锋与压缩波之间的局部区域反应剧烈,反应放热率明显增加,从而促使热点形成。形成的热点迅速放大成为过驱爆震波,并逐渐衰减为稳定爆震波。稳定爆震波阵面参数与CJ理论结果进行了对比,两者符合得较好。

Abstract:

Based on the modified wave propagation algorithm which is suitable for multi-component reactive flow, the numerical simulations of detonation initiation by two types of toroidal flame for methane-air mixture were performed in a tube. The distributions of pressure, temperature, chemical heat release and species concentration were calculated for both types of initial toroidal flame, and the formation and effectiveness of "hot spot" were discussed according to the calculated results. The results show that the compression wave produced by flame can collide and reflect on axis or wall of tube. The interaction between shock complex and flame accelerates the chemical heat release rate, and leads to the formation of hot spot. Further, the hot spot is amplified to form the overdriven detonation wave, then, the overdriven detonation wave gradually becomes the steady detonation wave. The calculated parameters of steady detonation wave front are compared with those of CJ theory, and the good agreements can be obtained.