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本文是研究后置式汽车发动机的进气条件对冷却风扇的气动噪声影响的系列文章之一。主要介绍进气紊流强度和尺度对轴流冷却风扇气动噪声的影响。试验是在上海交大涡轮机研究所的气动消声室内进行的。在自行设计搭建的实验台上测量了三种不同进气条件下风机进口紊流强度和紊流尺度、风机叶片的尾迹宽度及平均速度、压力等参数。噪声测量是在风机出口和风机中心，轴线同一平面内，距风机中心１ｍ处的很多点上进行的，并记录了总声级和４５°处风机噪声的１／３倍频程谱。试验结果表明，在所试验的条件下风机噪声谱呈现明显的宽频性质，且进气紊流噪声已超过尾涡脱落噪声成为风机的主要声源。试验还表明的高强度、小尺度（紊流强度１３．３％－２５．４％、紊流尺度１１．２ｍｍ—２８．５ｍｍ）的进气紊流条件下，紊流强度对噪声的影响远大于紊流尺度的影响。
This article is one of a series of articles that investigate the effect of air intake conditions on the cooling fan’s aerodynamic noise in a rear-mounted automotive engine. Introduce the influence of the turbulence intensity and scale of the intake air on the aerodynamic noise of the axial cooling fan. The test was conducted in the pneumatic silencing room of Shanghai Jiaotong University Turbine Institute. The turbulence intensity and turbulence scale of the fan inlet, the wake width and the average velocity, and pressure of the fan blade were measured on three experimental benches designed and built. The noise measurements were taken at many points on the same plane as the fan outlet and the center of the fan, on the axis, 1 m from the center of the fan, and the total sound level and 1/3 octave spectrum of the fan noise at 45° were recorded. The experimental results show that the fan noise spectrum exhibits obvious broadband characteristics under the tested conditions, and the intake turbulence noise has exceeded the tail vortex shedding noise to become the main sound source of the fan. The experiment also showed that the turbulence intensity has a great influence on the noise under the conditions of high-intensity, small-scale (turbulent intensity 13.3%-25.4%, turbulent flow 11.2mm-28.5mm) intake turbulence conditions. Impact on turbulence scales.