广义RNG湍流模型对柴油机低温燃烧预测的影响

The Effects of a Generalized RNG Turbulence Model on the Predictions of Low Temperature Combustion in Diesel Engine

基于湍流快速畸变理论和各向同性湍流的衰减分析,提出了一种广义RNG湍流模型,该模型的主要物理特征是其模型系数均被模拟为局部流场应变率张量的函数。为了考察广义RNG湍流模型对发动机缸内复杂化学反应流预测的影响,将该模型应用于一款采用部分预混压缩着火控制的低温燃烧直喷柴油机的缸内燃烧计算中。计算得到的柴油机缸内油气混合、燃烧放热和未燃碳氢排放物的生成及其发展历程与标准RNG模型的预测结果和实验结果进行了对比。结果表明:广义RNG模型预测的缸内UHC及其空间分布与实验结果吻合的更好。

Based on the rapid distortion theory and the isotropic turbulence decay analysis,a generalized RNG turbulence model is proposed with a physical feature that all its parameters are modeled as the functions of strain rate tensors in local flow field.For investigating its effects on the prediction of the in-cylinder complex chemical reaction flow of engine,the generalized RNG turbulence model is applied to the in-cylinder combustion calculation of a DI diesel engine operating in a low temperature combustion regime with partial pre-mixture compression ignition control.The in-cylinder fuel-air mixing,heat release and the generation and evolution history of unburned HC（UHC） are calculated and compared with the results predicted with standard RNG model and experimental data available.The results show that the in-cylinder UHC and its spatial distribution predicted by generalized RNG model are closer to experimental data compared with standard RNG model.