湍流扩散火焰中对基于混合分数的湍流燃烧模型的数值研究

摘要

Based on the similarity in the modeling approach, detailed numerical investigation of non-premixed flames is conducted to evaluate the unsteady flamelet model and the conditional moment closure (CMC). The involved test cases include H2/N2 and CH4/H2/N2 flames with different Reynolds number and turbulence-chemistry interactions. The Lagrangian extension of the flamelet model (LFM) and a cross-stream-integrated formulation of CMC are considered.Moreover, the predicted values of steady laminar flamelet model are also presented in the simulation of H2/N2 flame.For both flames, in terms of major species, the two models yield very similar results, which are in reasonable agreement with the experimental results, while agreement is less satisfactory for radical OH and NO. For the CH4/H2/N2 flame local extinction, the levels of NO are over-predicted by CMC and LFM by a factor of 2-3.%根据条件矩模型(CMC)和小火焰面模型在模型构建上的相似,针对具有不同大小雷诺数和湍流-化学相互作用特性的非预混湍流射流火焰,对这两种模型进行了数值研究和比较.湍流燃烧模型采用Lagrangian型非稳态小火焰模型(LFM)和径向加权积分的CMC模型,而在H2/N2火焰的数值研究中还考虑了稳态小火焰模型的数值模拟结果.数值结果表明,在两种火焰中这两种模型对主要组分的预测结果较为一致并与实验符合较好,而OH和NO的预测值差异明显;同时对于具有局部熄火特性的CH4/H2/N2火焰,NO的预测值被高估了2～3倍.