In this paper, the aerodynamic noise of a centrifugal fan with an eccentric impeller is investigated and analyzed by adopting a hybrid method combining detached-eddy simulation and the acoustic finite element method (FEM). The impeller-eccentric effect of high-speed centrifugal fans, frequently ignored in theoretical studies, is objective in practical engineering applications owing to machining and installation errors, which have a significant influence on flow characteristics and subsequently noise characteristics. An impeller-whirling model combined with the sliding mesh method is introduced to obtain the actual flow with an eccentric impeller. First, the internal flow field handled with different eccentricities is investigated. The total pressure and internal efficiency decline, and the flow field near the leading edge shows intense unsteadiness, inducing a rise in the pressure fluctuation amplitude at the rotating frequency (RF) in both impeller flow passage and volute domain. Second, the variational formulation of Lighthill’s analogy is implemented by acoustic FEM to better account for the interaction between the solid surface and aerodynamic sound, capturing a contribution by turbulence noise at the second RF. Under eccentric conditions, the sound source intensity shows a circumferential non-uniform distribution in a similar region to the flow field. The calculated sound pressure level captures the variation in the experimental result, which shows an obvious rise at RF induced by the impeller-eccentric effect. The characteristics of the noise spectrum and sound directivity change significantly, and the overall sound pressure level rises with the increase in eccentricity. This study provides an effective simulation strategy for predicting the aerodynamic noise of centrifugal fans under realistic conditions.

本文采用分离涡模拟与声学有限元法(FEM)相结合的混合方法对带偏心叶轮的离心风机气动噪声进行了研究分析。高速离心风机的叶轮偏心效应在理论研究中经常被忽视，但由于加工和安装误差在实际工程应用中是客观的，这对流动特性和随后的噪声特性有显着影响。引入叶轮-涡动模型结合滑动网格法得到偏心叶轮的实际流量。首先，研究了不同偏心率处理的内部流场。总压力和内部效率下降，前缘附近的流场表现出强烈的非定常性，导致叶轮流道和蜗壳域在旋转频率（RF）处的压力波动幅度都上升。其次，Lighthill 类比的变分公式由声学 FEM 实现，以更好地解释固体表面和空气动力声之间的相互作用，捕获第二个 RF 处湍流噪声的贡献。在偏心条件下，声源强度在与流场相似的区域呈圆周非均匀分布。计算的声压级捕捉到了实验结果的变化，表明叶轮偏心效应引起的 RF 明显升高。噪声频谱和声音指向性的特性发生显着变化，并且整体声压级随着偏心率的增加而上升。本研究为在现实条件下预测离心风机的气动噪声提供了一种有效的模拟策略。