尾缘锯齿降低叶栅噪声的数值模拟

采用大涡模拟与声类比的方法研究了尾缘锯齿对涡轮叶栅噪声的影响.设计了两种不同的尾缘锯齿,对比了Re=3.3×105(基于叶片弦长与叶栅出口速度)下两种不同结构锯齿尾缘叶栅与直尾缘叶栅的声功率.结果表明:尾缘锯齿可以降低叶片吸力面边界层分离噪声约5dB,降低尾缘涡脱落噪声约10dB.进一步的研究表明,尾缘锯齿可以降低叶片尾缘附近表面的压力脉动幅值约50%,将展向相关尺度较大的涡破碎成展向相关尺度较小的涡,并消除尾缘脱落涡,这三者的综合作用使噪声得到降低. 

Numerical simulation on noise reduction for the cascade with trailing edge serrations

Large eddy simulation and acoustic analogy were performed to investigate the effect of trailing edge serrations on the turbine cascade noise. Two different trailing edge were designed. Comparisons were made for the sound power of two different serrated trailing edge cascades and straight trailing edge cascade under Re=3.3×10⁵ (based on the blade chord and cascade outlet velocity).The result shows that the trailing edge serrations can reduce the blade suction surface boundary layer''s separation noise by about 5dB and the trailing edge vortex shedding noise by about 10dB. Further investigation shows that trailing edge can reduce blade surface pressure fluctuation amplitude by about 50% near the trailing edge and change the vortexes of large spanwise correlation length into those of smaller spanwise correlation length. Furthermore, the trailing edge serrations can eliminate the trailing edge vortex shedding. The above three factors work jointly and contribute to the final noise reduction.