柴油机废气涡轮增压器压气机的气动噪声源特性研究

Research on the noise mechanism and characteristics of the diesel engine turbocharger

基于雷诺时均方程(RANS)及双方程湍流模型,建立了船用大功率增压器压气机的内部流场计算模型;计算了压气机叶轮流道内的流速分布和湍流流场,得到叶片顶部出口附近的流速分布在1.02马赫和1.1马赫之间;采用基于声比拟的数值积分方法(FW-H方程),得到了压气机叶轮的气动噪声源,并比较了主叶片和分流叶片顶部出口位置的气动噪声频谱特征,发现两者的噪声级及叶频分布存在差异。计算表明:压气机在轴频及其谐波频率处的噪声远小于叶频噪声,主流叶片及分流叶片紊流的噪声成因不同;压气机内部流噪声源的大小主要取决于气流速度;压气机转速由8000r/min增加至16000r/min、由16000r/min增加至22000r/min,流噪声的幅值约增加12dB。

The computational model for the internal flow field of the high-power marine turbocharger compressor is built, which is based on the RANS equations and two-equation turbulence model. With this model, the velocity distribution and the turbulent flow field in the flow passage of the compressor are calculated and the results obtained indicated that the Mach number near the blade tip region at the outlet distributes between 1.02 and 1.1. The aerodynamic noise source of the impeller is obtained based on the numerical integration method of acoustic analogy(FW-H equation). The aerodynamic noise spectrum characteristics of the main blades and splitter blades at the blade tip region on the outlet section are compared, the noise level and blade passing frequency(BPF) are differenet between them. The result show that the noise at the shaft frequency and its harmonic components is much lower than the BPF noise, the contributing factor of the turbulence noise of the main blades and splitter blades is different. Meanwhile, the magnitude of the noise source mainly depends on the velocity magnitude and the aerodynamic noise increased by about 12 dB when the rotating speed of the compressor is doubled.