汽车交流发电机端盖栅格对其气动噪声和温度特性的综合影响

为了同步提高目前新能源汽车发电机的气动噪声性能和散热效果，满足更严苛的噪声、振动与声振粗糙度需求，以某型汽车交流发电机为研究对象，基于台架试验和数值仿真方法探究端盖栅格对气动噪声和温度场分布的综合影响规律；基于五点法获得了噪声声压级分布，基于多热电偶测点获得了关键部件的温度分布，基于计算流体动力学仿真软件和电磁场Maxwell仿真软件获得了发电机内部的流场、声场和温度场分布，采用试验结果验证数值计算模型的正确性；在分析原始发电机气动噪声特性和温度场特性的基础上，设计了具有不同倾角的端盖栅格侧壁以降低冷却气流冲击的动能损失，探讨了端盖栅格倾角和扇叶气流出口角的合理匹配，并基于牛顿冷却理论研究了波状端盖栅格对增加换热表面面积和降低气动噪声的影响。研究结果表明:端盖栅格结构对气动噪声有较大贡献，同时也对冷却效果产生显著影响；端盖栅格侧壁倾斜40°时能够和扇叶气流出口角更合理地匹配，有效减少冷却气流冲击的能量损失，三相定子绕组最高温度降低9.63 K，12阶次气动噪声降低3 dB(A)以上；波纹状端盖栅格增加对流换热面积和气流速度的同时降低了气动冲击作用，使得端盖散热量增加7.72 W，定子铁芯、端盖和三相定子绕组温度分别降低了5.12、4.94和5.29 K，栅格对涡流的改善以及气流对栅格的冲击削弱使12和24阶次气动噪声降低3 dB(A)以上。 

Comprehensive influences of end cover grid on aerodynamic noise and temperature characteristics of an automobile alternator

To synchronically improve the aerodynamic noise performance and heat dissipation effect of the current alternator of new energy vehicles and meet the more stringent noise-, vibration-, and harshness- requirements. An alternator was taken as the research object, the comprehensive influence laws of end cover grids on the aerodynamic noise and temperature field distribution were analyzed by the bench experiment and numerical simulation method. The sound pressure level (SPL) distribution of noise was obtained by the five-point method, and the temperature distribution of key components was acquired on the basis of multi-thermocouple measurement points. The flow field, sound field, and temperature field distributions of the alternator were obtained by the computational fluid dynamics simulation software and electromagnetic Maxwell simulation software. The correctness of the numerical calculation model was verified by the experimental results. Upon the analysis of aerodynamic noise characteristics and temperature field characteristics of the original generator, the end covers with different angles of grid side walls were designed to reduce the kinetic energy loss caused by the cooling airflow impact. The reasonable matching of end cover grid angles and fan-blade airflow outlet angles was discussed, and with Newton's law of cooling, the effects of wavy end cover grids on the increase in the area of heat transfer surface and the reduction in aerodynamic noise were studied. Research results show that the end cover grid structure has a great contribution to the aerodynamic noise, and the cooling effect is also significantly affected by the structure. When the side wall of the end cover grid inclines at an angle of 40, a more reasonable match can be achieved with the airflow outlet angle of the fan blade, the energy loss caused by the cooling airflow impact can be effectively reduced. The maximum temperature of the three-phase stator winding reduces by 9.63 K, and the 12th-order aerodynamic noise lessenes by more than 3 dB(A). The wavy end cover grid increases the convective heat transfer area and airflow velocity, while reducing the aerodynamic impact. The heat dissipation of the end cover increases by 7.72 W, and the temperatures of stator core, end cover, and three-phase stator winding decrease by 5.12, 4.94, and 5.29 K, respectively. The 12th-order and 24th-order aerodynamic noises reduce by more than 3 dB(A) with the improvement in eddy currents by grids and the reduction of airflow impact on the grids. 4 tabs, 25 figs, 31 refs.