压燃式天然气发动机燃烧过程CFD模拟计算中的若干问题

化学动力学机理、燃烧模型类型以及网格数量等对CFD计算结果、计算过程收敛性及计算机时有十分重要的影响．针对一台新开发的压燃式天然气发动机的燃烧过程进行了较为深入的CFD模拟计算研究,分析对比了化学动力学机理、燃烧模型类型、网格数量以及计算步长取不同值或采用不同种类时对模拟计算的影响．结果表明,合理的简化机理既可以节省机时又有较好的计算精度；多维模型由于考虑了流场内温度场的不均匀性以及传热现象,计算结果与实测值比较吻合；网格数量主要影响计算的精度和计算机时,需要折中考虑．

Some Problems Occurred in Numerical Simulation of Combustion Process in a Compressed Ignition Natural Gas Engine

Chemical kinetic mechanism,combustion model type and grid number have a strong influence on the results, convergence and CPU time of compatational fluid dynamics (CFD) simulation.A numerical study on a new developed com- pression ignition natural gas engine was completed intensively and comparisons were made between the simulating results when different chemical mechanism,combustion models and grid numbers were used.It is shown that the reduced mecha- nism can save CPU time and enhance accuracy in prediction.The results obtain by multi-dimensional model are in good a- greement with the experimental data because temperature inhomogeneity and heat transfer were considered.Grid numbers mainly influence accuracy and CPU time,so a trade-off must be considered.