数值方法在轴流式风机气动噪声识别中的应用

摘要

The numerical simulation on the aeroacoustic noise of the small axial-flow fan is conducted using the unsteady flow field calculation and acoustic analog method based on FWH equation.The test device is set up to study the noise characteristics of the axial flow fan in the anechoic chamber.The virtual anechoic chamber which has the same size with the real one is used for numerical simulation.The simulation gets the best result at the condition of LES model,23 million mesh,and the time cost by 1°/cycle for fan as time-step.In this condition,the simulation results agree well with the experimental data in the noise frequency of 200～1 000 Hz.With the further investigation,through the analysis on the noise sources from the separating effect,the interaction between the rotating blade and separated flow,and the vortex around the tip of blade,it's found that the main noise sources are the apex of leading edge,the tip of blade and the center of blade,whose frequencies are 200～500 Hz,500～1 000 Hz and around 800 Hz,respectively.%采用非定常流场计算和基于FWH方程的声学类比方法对小型轴流式风机的气动噪声进行数值仿真研究,并在消声室中建立轴流式风机的测试装置研究其噪声特征.数值模拟中的虚拟消声室的大小与实物大小相同,选取最优计算工况为LES模型、2 300万网格及时间步长为叶轮转过1°所需时间,通过与试验对比,在噪声频率200～1 000 Hz范围内,计算结果与试验结果有较好的吻合.在此基础上,对分离作用、旋转叶片和分离流的相互作用、叶尖处涡流等叶片噪声源进行分析,发现噪声源主要来自叶片前缘的顶部位置、叶尖位置以及叶片中心区域,这3个区域产生的噪声频率分别在200～500 Hz,500～1 100 Hz以及800 Hz左右.