车用交流发电机气动噪声数值分析

Numerical simulation analysis for aerodynamic noise of a vehicle alternator

以某型车用交流发电机(也称爪极发电机)为研究对象,采用计算流体力学技术对交流发电机的空气动力学特征进行了三维非定常数值模拟,应用滑移网格技术和大涡模拟方法对交流发电机进行气动噪声特性研究。得到大涡模拟在交流发电机噪声数值预测方面其主要阶次和对应的幅值与试验对比有很好的一致性;前后扇叶为该型交流发电机的气动噪声声源;第6、8、10、12和18等阶次为该型交流发电机的主要气动噪声成分。在数值模拟基础上,以低噪声、高流量为优化目标,对交流发电机前端盖径向栅格分布角度进行气动噪声优化设计及降噪研究。得到前端盖径向栅格倾斜40°分布角度时交流发电机远场气动噪声最低、质量流量最大。所得研究成果可为车用交流发电机的气动性能和高转速下噪声的改进提供一种切实可行的参考依据。

The 3-dimensional aerodynamic noise characteristics of a certain vehicle alternator （claw-pole alternator） were simulated numerically with computational fluid dynamics technique. The sliding mesh technology and large eddy simulation （LES） were used to study the aerodynamic noise of the alternator. It was shown that the numerical predictions for orders of noise and their amplitudes obtained with LES are in good accordance with experimental results; the front and rear blades are the aerodynamic noise sources for this type of alternator; the main components of aerodynamic noise are the 6th, 8＇h, 10tll, 12th and 18th orders. On the basis of numerical simulation, taking low noise and high flow rate as optimization objectives, the optimal design and noise reduction of aerodynamic noise for the angle distribution of the front end cover radial grid performed. After sloping the front end cover radial grid to 40~ angle, it was shown that not only the total noise is lowest but also the mass flow rate is highest. The results provided a reference for the improvement of aerodynamic performance and high speed noise of vehicle alternators.