用ASOM和PDF方程模型模拟湍流射流燃烧

Comparison of the ASOM Model and the PDF Transport Equation Model in Simulating Turbulent Jet Combustion

分别用代数二阶矩(ASOM)湍流燃烧模型和概率密度函数(PDF)输运方程模型模拟了美国Sandia国家实验室测量的甲烷-空气湍流射流燃烧,并将模拟结果与实验结果对比.结果表明,在大多数区域内,两种模型预报的平均温度、平均组分质量分数都与实验结果符合很好,考虑到ASOM模型的计算量约为PDF方程模拟计算量的1/100,因而认为ASOM模型更适合工程应用.用PDF模拟结果统计的温度和质量分数脉动的自关联,以及反应速率系数脉动和质量分数脉动的互关联,在大多数区域内与对应的时均量的梯度乘积有相似的变化趋势,因此验证了ASOM模型封闭假设的合理性。

A composition probability density function transport equation （PDF） modal and an algebraic second-order moment （ASOM） model of turbulent combustion are used to simulate a methane-air turbulent jet flame, measured by Sandia National Laboratory. The prediction results are then compared with the experimental data, which shows that the predicted time-averaged temperature and species concentration using both of the models are,in most region,in good agreement with the experimental data. Considering that the computation time of the PDF model is approximately 100 times that of the ASOM model, the ASOM model is considered to be mere suitable for engineering application. The statistical results of the PDF model predictions show that the correlations of the methane concentration fluctuation with the oxygen concentration fluctuation, of the temperature fluctuation with the methane/ oxygen concentration fluctuation, and of the reaction-rate coefficient fluctuation with the methane/oxygen concentration fluctuation, show the similar trends with the products of the gradients of corresponding time-averaged variables,hence validating the closure assumptions made in the ASOM model.