轴流风机非稳态气动声学建模及分析

Modeling and Analysis of Unsteady Aeroacoustics of Axial Fan

轴流风机作为应用广泛的流体机械,其声学性能逐渐受到人们重视。本文以某轴流风机为研究对象,结合计算流体力学和计算气动声学理论对轴流风机的声场进行数值模拟,利用雷诺时均(RANS)模型进行稳态流场模拟,通过在风机进口、出口和叶片表面上布置监测点,研究了风机在近场流域内的声源分布特性及声场变化趋势;利用大涡模拟(LES)非稳态流场和Ffowcs Williams-Hawkings声类比模型结合的方法,通过在风机流场外设置声接收器,对流域外的声场进行积分预测,同时,本文进行了相关实验,验证了数值仿真的准确性。研究发现,轴流风机的主要噪声来自偶极子源,主要原因是由于压力梯度的变化;近场中,风机的噪声在靠近叶片的地方出现相对较大的声压,噪音通过远距离的传播,声压在全频段上整体减小,但衰减趋势不变。

As a widely used fluid machinery, the acoustical performance of axial flow fans has been paid more and more attention. In this paper, an axial fan is taken as the research object, and the sound field of the axial fan is numerically simulated by combining computational fluid dynamics and computational aero-acoustics theory to obtain the sound source distribution and acoustical law in the fan basin. The steady-state flow field was simulated by using the Reynolds time-mean (RANS) model. By setting monitoring points on the inlet, outlet and blade surface of the fan, the characteristics of the sound source distribution and the variation of the fan sound field in the near field basin were studied. By combining large eddy simulation (LES) unsteady flow with Ffowcs Williams-Hawkings acoustic model, the acoustic field was predicted through an acoustic receiver which was set up outside the fan flow field. Meanwhile, the accuracy of the numerical simulation was verified by relevant experiments. It is found that the main noise of axial fan comes from dipole source, which is mainly due to the change of pressure gradient. In the near field, the noise of the fan appears relatively large sound pressure near the blade. The noise propagates over a long distance, and the sound pressure decreases in the whole frequency band, but the attenuation trend remains unchanged.