受限空间内激波与火焰作用的三维计算

Three-Dimensional Computation of the Interactions Between Shock Waves and Flame in a Confined Space

关键词:  入射激波  反射激波  火焰  不稳定性  单步反应模型

Key words:  Incident shock wave  Reflected shock wave  Flame  Instability  Single-step chemistry model

摘要:

激波与火焰的相互作用常发生在超声速燃烧和燃烧转爆轰过程中,为深入了解这一现象,采用带化学反应的三维Navier-Stokes方程,对平面入射激波及其反射激波与火焰的作用进行了计算研究,其中燃烧过程使用单步反应模型描述。研究结果显示:在受限空间内模拟激波与火焰作用,能更好地符合实验结果,从而体现出受限空间的三维效应；火焰在入射激波的作用下主要经Richtmyer-Meshkov不稳定而发生变形,此时火焰变形以物理作用为主,燃烧膨胀效果相对不明显；当反射激波与变形火焰再次作用后,火焰迅速膨胀变形,放热率维持在较高水平,此时化学反应过程起主要作用；在反射激波的作用下,变形火焰复杂三维涡结构的形成能强化热量与质量的输送,提高燃烧速率。

Abstract:

The interaction between shock wave and flame occurs frequently in supersonic combustion and deflagration-to-detonation. To further understand the phenomenon, a computational study of the interactions between a planar incident shock wave and its reflected shock wave with a spherical flame was carried out by using the three-dimensional Navier-Stokes equations coupled with a chemical reaction, in which the combustion process was described by a single-step chemistry model. It can be found that the numerical simulation of the interactions between shock waves and flame agrees well with the experimental results in a confined space which embodies the three-dimensional effect of the numerical simulation. When the flame interacts with the incident shock wave, it deforms through Richtmyer-Meshkov instability. In this case, the physical process takes an important role and the flame expansion is relatively not obvious. While the deformed flame interacts with the reflected shock wave again, the flame expands rapidly, and maintains the heat release rate at a high level, which suggests that the chemistry reaction plays an important role in this stage. With the action of reflected shock wave, formation of complicated vortex structure of deformed flame can enhance the transport of heat and mass, and therefore can raise the burning rate.