预混燃烧中CMC亚模型的先验性分析

A Priori Analysis of CMC Sub-Models in Premixed Combustion

本文用直接数值模拟的方法对各项同性湍流中的H_2/air平面火焰进行了研究。模拟了当量比分别为0.6和1.0的两种预混火焰,采用了9种组分19步反应的详细机理.对预混燃烧中的CMC亚模型进行了先验性分析.发现clipped Gaussian和Beta function两种方法都能定性描述过程变量的概率分布,但是Beta function的结果与直接数值模拟更接近.AMC和Girimaji两种模型都能较好地模拟标量耗散率的条件平均分布,在贫燃的情况下模型预测的结果更接近直接数值模拟的结果。

Direct numerical simulation is employed to study H2/air planar premixed flames in decaying isotropic turbulence. Two cases with equivalence ratios of 0.6 and 1.0 are investigated. A 9 species and 19-step reduced mechanism for H2/air combustion is adopted. The CMC sub-models are validated in an a priori sense. It is found that both the clipped Gaussian and the Beta function can be used to describe the probability density function （PDF）, and the predictions by the Beta function are closer to the DNS results. The scalar dissipation rate is modelled using the amplitude mapping closure （AMC） model and the Girimaji model. It is found that the performances of the models are better in the fuel-lean case.