高压湍流燃烧中组分扩散的数值研究

Numerical Study of Molecular Diffusion in High Pressure Turbulent Combustion

本文通过分析高压对流扩散湍流燃烧直接数值模拟的高精度结果,研究了复杂燃烧反应中组分扩散过程。在直接数值模拟中,本文使用的组分扩散项在Fick扩散的基础上添加了不同组分扩散、Soret扩散、Dufour扩散、和多组分扩散。计算对比分析了组分扩散在不同环境压力和雷诺数下的区别。此外,为了能够量化的研究高压下组分扩散对燃烧造成的影响,本文推导了用于简化计算的有效扩散因子模型。结果显示,在超过临界压力的情况下,不同组分扩散效应十分显著.且相较于浓度高且分子量大的组分,燃烧过程中产生的低浓度小分子量的组分更易受到其他组分浓度梯度、压力梯度和温度梯度的影响.

This article analyzed high fidelity Direction Numerical Simulation （DNS） results of a high pressure turbulent flame in mixing layer, and studied the molecular diffusion process under complex chemical reactions. In the DNS, besides Fick diffusion, the molecular diffusion also includes differential diffusion, Sorer diffusion, Dufour diffusion, and multicomponent diffusion. The molecular diffusion term under varies pressure and Reynolds are analyzed. In addition, to quantify the molecular diffusion influence on combustion at large pressure, this article derived an effective molecular diffusion model. Results show, at large pressure above supercritical pressure, the differential diffusion is significant. Compared with the species having large concentration and molecular weight, the intermediate species with small concentration and molecular weight is more influenced by the other species concentration gradient, pressure gradient and temperature gradient.