Soret扩散对层流火焰的影响

Effects of Soret diffusion on laminar flames

在层流火焰中,各个组分的质量扩散具有十分重要的作用,它能够影响甚至控制火焰传播、点火、熄火等过程.通常由浓度梯度引起的Fick扩散是占主导地位的,而由温度梯度引起的Soret扩散则相对较小.因此,在理论分析和数值模拟中,通常只考虑Fick扩散而忽略Soret扩散.但是,以往的研究结果表明,对于氢气或大分子碳氢燃料的层流燃烧过程,当存在较大温度梯度时,Soret扩散的影响不可忽略.本文回顾了Soret扩散影响层流火焰的相关研究,主要介绍了Soret扩散对(1)无拉伸和有拉伸预混火焰的传播速度、点火与熄火,(2)扩散火焰的结构与熄火,以及(3)喷雾燃烧和碳烟生成的影响.

Mass diffusion plays a critical role in laminar flames. It affects and even controls flame propagation, ignition and extinction. Usually Ficikan diffusion driven by concentration gradient is dominant while Soret diffusion driven by temperature gradient is relatively small. Therefore, in theoretical analysis and numerical simulation, only Fickian diffusion is considered and Soret diffusion is neglected. However, previous studies indicated that Soret diffusion cannot be neglected for cases with sufficiently light or heavy species and strong temperature gradients. This paper reviews the effects of Soret diffusion on laminar flames. Specifically, we discuss the influence of Soret diffusion on（1） flame propagation, ignition and extinction of premixed planar flames and stretched flames,（2） flame structure and extinction of non-premixed flames, and（3） spray combustion and soot formation.