倾斜/后掠叶片对风扇单音噪声的控制研究

Control of Tonal Noise in an Axial Flow Fan withRotor Tip Clearance，Stator Lean and Sweep

关键词:  混合模型  声类比  单音噪声  叶尖间隙  倾斜/后掠静子叶片

Key words:  Hybrid model  Acoustic analogy  Tonal noise reduction  Tip clearance  Leaned/swept stator vane

摘要:

为探索倾斜/后掠静子叶片对风扇单音噪声的降噪机理并指导低噪声风扇的设计，采用基于三维黏性非定常雷诺平均数值模拟(URANS)和管道声类比理论(Ducted Acoustic Analogy，DAA)的流场/声场混合计算模型(CFD/AA)研究了不同转子叶尖间隙、倾斜静子、后掠静子等对NPU-Fan单音噪声的影响。计算结果表明:随着叶尖间隙增加，在1BPF(Blade Passing Frequency)和2BPF处，风扇前传、后传气动噪声均会增加，且1BPF处单音噪声增量大于其它谐频。在研究倾斜及后掠叶片的降噪机制时，须将管道特征函数与声源的耦合过程包含在内，并且要考虑真实风扇的尾迹特性及其向下游的输运过程。风扇静子负倾斜可以提升风扇的气动效率，但会增加噪声的声功率级；正倾斜叶片能够降低噪声声功率级，但风扇气动性能会有所降低。随着倾斜角的增加，降噪量增大，当倾斜角为+30°时，各谐波阶次的降噪量均超过2.3dB。后掠静子叶片相较于倾斜设计具有更好的气动性能和降噪效果。30°后掠角对于各谐波阶次的前传噪声降噪量均大于6.3dB，降低后传噪声超过10dB。正倾斜及后掠静子的降噪效果与噪声谐波阶次、传播方向紧密相关，谐波阶次越高，降噪效果越明显。倾斜-后掠综合设计方案对于前传噪声拥有最好的降噪效果，其综合了倾斜和后掠两者的优点。

Abstract:

In order to investigate the noise reduction of fan tonal noise by leaned/swept stator vane and guide the design of low-noise fan， a hybrid flow/acoustic field computational model is used to analyze the tonal noise characteristics of the NPU-Fan with different rotor tip clearances， various leaned and swept stators. This hybrid model combines numerical simulation based on the three dimensional unsteady Reynolds-Average Navier-Stokes (URANS) equations and the ducted acoustic analogy (DAA) theory. Numerical results show that with the increasing of tip clearance， both upstream and downstream propagating noise will increase at 1BPF (Blade Passing Frequency) and 2BPF， and this tonal noise increase is more pronounced at 1BPF than at other harmonics. The influence of the eigenfunction in the annual duct， the wake characteristics of the real fan and the wake transport process should be taken into account in analyzing the noise reduction mechanism of swept/leaned stator. The negative leaned stator can improve fan aerodynamic performance and increase both upstream and downstream tonal noise. The positive leaned stator reduces sound power with growing angles; and for 30° leaned angle， the noise reduction exceeds 2.3dB at all harmonics. Compared with leaned stators， the swept stators lead to better aerodynamic and acoustic performance. The 30° swept stator can reduce the upstream noise and downstream noise by more than 6.3dB and 10dB respectively for all harmonics. The noise reduction effect of positive leaned and swept stator is closely related to the order of harmonics and propagation direction. And the higher the harmonics， the better the noise reduction effect. The leaned-swept stator combines the advantages of the leaned stator and swept stator and leads to the best noise reduction for the upstream noise.