考虑多参数影响的增压发动机现象学爆震预测模型

A Phenomenological Model for Predicting Knock Onset of the Turbocharged Engine Considering the Effects of Multi-Parameters

针对发动机概念设计一维性能仿真优化阶段爆震约束问题,使用末端混合气自着火延迟期积分法,提出一个同时考虑温度、压力、废气再循环(EGR)率和空燃比影响的爆震预测模型。在一台带冷却EGR系统的增压汽油机上进行爆震试验,使用滤波法和图像处理方法提取爆震特征。采用绝热压缩求解每个爆震循环末端混合气温度,并探讨比热比的影响及比热比求解方法对末端混合气温度的影响。结合多岛遗传算法对爆震模型系数进行标定,并与经典模型就预测性能进行对比。结果表明,提高进气温度或加浓混合气都会减小混合气比热比,而引入冷却EGR则会增加混合气比热比。采用定比热比得出的末端混合气温度会大幅高于变比热比得出的末端混合气温度。Douaud模型预测误差随EGR率增加而增大,而考虑多参数影响的爆震模型预测性能较好。

In order to consider the knock constrain when dealing with the 1D engine performance simulation during the concept design stage, a predictive knock model was developed based on the integration of the ignition delay of the end mixture, considering the effects of temperature, pressure, EGR and air-fuel ratio. The knock experiments were conducted using a turbo-charged gasoline engine equipped with cooled EGR system, and the knock characteristics were captured with signal filtering and image processing method. The end gas temperature of each knock cycle was calculated by an isotropic compressing equation, considering the impact of parameters on specific heat ratio, and the impact of specific heat ratio solving method on end gas temperature. The new model was calibrated with multi-island generic algorithm, and the predicting accuracy of the new model was compared with that of the classical model. The smilation results show that increasing the intake temperature or enriching the mixture can decrease the specific heat ratio of the mixture, while using cooled EGR can result in increased specific heat ratio. The end gas temperature with constant specific heat ratio, is higher than that with variable specific heat ratio. The predicting error will get larger with an increase in the EGR rate for the Douaud model, while the new knock model considering the influence of multi-parameters has good predictive performance.