考虑来流偏角的汽车道路行驶阻力研究

Study on Vehicle Road Resistance Considering Incoming Flow Yaw Angle

汽车日益严苛的排放、油耗法规对准确测量和降低道路行驶阻力提出了更高的要求,气动阻力是汽车道路行驶过程中主要的阻力来源,真实道路自然风来流偏角是影响汽车气动阻力的重要因素。提出了一种基于真实道路来流偏角分布的风平均阻力系数计算方法——偏航角密度法,并和其他风平均阻力系数计算方法进行了比较,利用风洞法测量道路行驶阻力,研究了来流偏角对汽车道路行驶阻力、循环能耗的影响。研究表明,来流偏角概率密度呈现明显的区域分布特征,来流偏角显著影响汽车实际道路气动阻力、循环能耗,根据偏航角密度法,考虑真实道路来流偏角时,气动阻力、循环能耗分别最大可增加3.0%、1.6%。

The increasingly strict regulations for vehicle emissions and fuel consumption put forward higher requirements for accurate measurement of vehicle running resistance and reduction of the resistance.Aerodynamic drag,affected mainly by the wind yaw angle,is the primary vehicle resistance force at moderate and higher speeds.In this paper,the yaw angle density method was proposed to calculate the averaged wind drag coefficient based on the yaw angle distribution of the incoming flow.The proposed method was compared with other existing methods as well.The wind tunnel method was applied to analyze the influence of the incoming flow yaw angle on the road resistance and the energy consumption based on driving cycles.The results show that the probability density of the incoming flow yaw angle is presented and the yaw angle significantly affects the actual aerodynamic drag and the energy consumption.According to the yaw angle density method,the aerodynamic drag and the energy consumption can be increased by 3.0%and 1.6%respectively.