Numerical research on aerodynamic radiation noises of alternators in vehicles

Abstract

To study the aerodynamic noise characteristics of alternators in vehicles, this paper established a computational model for the aerodynamic noise of an alternator based on computational fluid dynamics (CFD). The alternator adopted a non-scaling model and considered the detailed structure of collectors and other parts. Based on Lighthill acoustic theory, this paper adopted three-dimensional and large eddy simulation (LES) to conduct an unsteady numerical simulation for the flow field around the alternator, and Ffowcs Williams-Hawkings (FW-H) model was then adopted to conduct an unsteady computation for the aerodynamic noise of the alternator in the far field. When the rotational speed of the alternator was 10000 r/min, this paper obtained the aerodynamic noise characteristics of the alternator and the unsteady flow field structure around the alternator. Studied results showed: The main aerodynamic noise sources of the alternator were front fan, rear fan and stator structure; main influence orders of aerodynamic noises were the 6th, 8th, 10th, 12th, 18th, 24th, 30th and 36th orders. Similarly, this paper also conducted an experimental test on the noise of vehicle alternators. The main influence orders of aerodynamic noises of alternators were the 6th, 8th, 10th, 12th, 18th, 24th, 30th and 36th orders, which was consistent with the working condition of numerical simulation. It showed the correctness of computational results in this paper. In addition, this paper adopted the method of vector synthesis and the distribution of fan blades of the alternator to explain the cause of various orders and provided engineering application foundation for further reducing the noise of main orders.