基于排气凸轮轴选型试验的数据分析与研究

Data Analysis and Research Based on Exhaust Camshaft Type Selection Test

以某1.5T发动机开发过程中两款凸轮轴选型试验结果为基础,结合理论计算,分别对比不同排气凸轮轴包角对发动机性能的影响;结合排气过程中的排气量模拟计算,对比分析两种排气凸轮型线在低速和高速时的换气过程。结果表明,排气凸轮轴包角越大,充气效率越高,高速段性能越好,但相应低速段废气回流越严重,不利于低速性能;随着转速/流量的增加,亚临界状态下的排气量比重明显增加。

In this article, the influence of different camshaft angles on engine performance is compared based on type selection test result of two camshafts during the development of a 1.5T engine, and in combination of theoretical calculation. The gas exchange process of two exhaust cam profiles in high and low speed is compared and analyzed based on simulative calculation of exhaust gas in the exhaust process. The result show that： the larger the camshaft angle, the higher the charge efficiency, and the better performance in high speed road will be, whereas the worse the exhaust gas return in low speed driving, therefore this design is not good for low speed. The phenomenon also shows that the ratio of discharged exhaust gas rises remarkably in subcritieal condition as the speed/flow increases.