民用航空发动机外涵支板声衬的降噪技术研究

为了研究民用大涵道比涡扇发动机风扇外涵支板对风扇转静干涉噪声后传声散射效应的影响,以及外涵支板布置声衬的降噪效果,本文基于有限元方法,首先研究了等截面圆形管道和环形的声传播和远场声辐射特性,并与解析结果进行对比,吻合地较好,表明了该声传播计算方法的可靠性和精度；然后开展对于包含外涵支板的某真实大涵道比涡扇发动机外涵管道的风扇转静干涉噪声后传声分析,最后开展外涵支板声衬的声阻抗优化设计,在约束条件内获得最优声阻抗,研究外涵支板布置声衬对风扇转静干涉噪声后传声的降噪效果。结果表明：有外涵支板的情况下,声波在管道内出现声散射现象,声压幅值较无支板情况明显增大,且在支板附近出现峰值；外涵支板布置声衬后,在最优声阻抗的情况下,单频单模态的降噪量可达22.57dB。

Noise reduction research on bypass Strut acoustic liner of the High Bypass Ratio Turbofan Engine

In order to investigate the effects of bypass strut on aft fan noise propagation of the high bypass ratio turbofan engine, and the noise reduction effect of bypass strut acoustic liner, the numerical simulation of this paper is based on finite element method. Firstly, the uniform section circular duct and annular duct are selected for numerical validations. The simulation results are well-matched with analytical results. Then the numerical simulation of aft fan noise propagation of a real high bypass ratio turbofan engine is calculated. At last the bypass strut acoustic liner optimization design is done in constraint condition to gain the optimal acoustic impedance. The results show that for the reason of bypass strut, acoustic scattering appears and the amplitude increases, the peak occurs nearby the bypass strut, and for single frequency and single acoustic mode, the insertion loss of bypass strut acoustic line with optimal acoustic impedance can reach 22.57dB.