用单循环分析法和集总平均法描述内燃机缸内湍流运动的差别

Differences between Two Methods of Cycle-Resolved Analysis and Ensemble Average in Describing Turbulence Motion in Cylinder of an Internal Combustion Engine

一般用热线风速仪或激光多普勒测速仪测量内燃机缸内的湍流运动,并用集总平均法求取湍流运动的平均速度和湍流强度。本文论述了用单循环分析法描述缸内湍流运动的理论,介绍了时间平均和低通滤波两种单循环分析方法,着重讨论了用单循环分析法和集总平均法计算湍流结构参数的差别。分析认为,集总平均法和单循环分析法分别依据湍流分量中包含还是不包含整体速度的循环变动速度分量来描述湍流运动,两种方法结合起来才能更详细地分析湍流运动的规律。

Generally, turbulence motion in the cylinder of an internal combustion engine is measured by hot wire anemometer or laser-doppler anemometer, and average speed and turbulence intensity are calculated by ensemble average method (EA). In this paper, the theory of cycle-resolved analysis method (CRA) was used to describe in-cylinder turbulence motion and two methods of CRA, time-average and low-pass filter, were introduced. Differences between two methods of EA and CRA in calculating turbulence structure parameters were compared. The results show that EA and CRA describe turbulence motion according to whether or not including low-frequence or larger- scale cycle-to-cycle variation in flow field, and combination of these two methods can analyze turbulent motion in more detail.