基于化学动力学模型的汽油机缸内过程数值仿真

In-Cylinder Process Simulation of an SI Engine Based on Gasoline Surrogate Kinetic Model

通过Kong模型,在CFD软件中实现了湍流与反应混合效应的模拟,并对一台MR479q发动机的缸内燃烧过程进行了仿真研究.为耦合化学反应过程,提出了一种新的适用于汽油机缸内过程仿真的汽油替代燃料化学反应机理,并用试验数据对该机理的着火延迟特性及火焰传播特性进行了验证.随后,将该机理与汽油机缸内CFD模型进行耦合计算,实现了对MR479q发动机的缸内燃烧过程的仿真.缸内压力计算结果表明:在2,000,r/min时,仿真计算的缸内平均压力与台架测得的数据基本一致.从缸内温度和密度分布的变化可以推论出:在点火之后,火焰传播快速发生,且火焰向进气门方向的传播速度较大.结果表明:CO排放随发动机转速升高而升高,NOx排放随转速升高而减少,并且仿真计算结果与试验结果趋势一致.

Using the Kong model,the combined effects of turbulence and kinetics were simulated in the CFD software. In-cylinder combustion process of an MR479 q engine was simulated. A new mechanism for gasoline surrogates was proposed and its ignition delay and flame speed were validated with the experimental results from literatures. The mechanism was applied in the CFD simulation of an in-cylinder process of the tested engine. The simulated in-cylinder pressure agrees well with the experimental data at 2,000,r/min. In-cylinder temperature and density indicate that flame develops rapidly after spark ignition and flame propagates fast toward the direction of intake valves. Results of emissions show that CO emission increases and NOx emission decreases with the increase of engine speed. Both CO and NOx emissions match well with the bench test results.