发动机泄气制动数值模拟及其性能优化研究

为优化发动机泄气制动性能,用UG软件建立了三维模型,应用动态网格技术对模型进行了网格划分并对气门和活塞的运动规律进行设置和定义.用Fluent软件对泄气制动工作过程进行三维瞬态数值模拟,分析了泄气制动过程活塞压力变化情况,并根据活塞瞬时受力得到各状态下发动机平均制动功率,得出排气背压、排气门开度、发动机转速对制动性能的影响.通过优化工作参数,提高了泄气制动性能,最后进行实验验证,结果表明最大误差为5.2%,最小误差仅为4.1%,表明模拟结果有较高精度和准确性.

Research on the Numerical Simulation and Performance Optimization of Engine Bleeding Brake

In order to optimize the performance of engine bleeding brake, a three-dimensional model was built with UG. The model was divided into grid by the dynamic mesh technique. Besides, the motion rule of the intake valve and piston was set and defined. By applying the three-dimensional transient numerical simulation in the process of engine brake working by Fluent, the changes of pition pressure were analyzed. According to the piston's instantaneous force, the engine average braking power in different conditions was calculated, and then the influence of exhaust valve lash, engine speed and exhaust back pressure on engine braking performance was also obtained. By optimizing working parameters, the performance of engine bleeding brake was enhanced, and the simulation results were verified with experiments. The results have shown that the maximum error is 5.2%, and the smallest error is only 4.1%. It is shown that the simulation results are of high precision and accuracy.