本文利用稳态气流的变更方程,建立了风机叶轮的转移矩阵。这是多级叶轮气流系统离散性频率声学特性的一个基衣公式。为了讨论离散性频率噪声,本文提出了多叶叶道流速激发的概念和计算公式。与风机负荷的波动相关,风机转子的角速度变化及相伴的低频拍振是不可避免的。本文还推荐了一些降低拍振振幅的措施。 In this paper, the change equation of steady state airflow is used to establish the transfer matrix of fan impeller. This is a base coat formula for the discrete frequency acoustics of multi-stage impeller airflow systems. In order to discuss discrete frequency noise, this paper proposes the concept and calculation formula of multi-leaf flow velocity excitation. In connection with the fluctuation of fan load, the change of the angular velocity of fan rotor and accompanying low frequency beat vibration are inevitable. This article also recommends some measures to reduce the beat amplitude.