轴向间距对单级风扇纯音噪声的影响

An integrated computational approach was introduced for prediction of single-stage fan tonal noise. The nonlinear harmonic (NLH) method was used for computation of acoustic sources，the incidence wave in the free field was based on acoustic analogy，and the scattering wave generated by boundaries was solved by boundary integral element method (BIEM). The sound propagation inside the duct and radiation outside the duct can be predicted simultaneously. Then，the present method was applied to tonal noise prediction of the Advanced Noise Control Fan (ANCF) developed by NASA Glenn Research Center. The effect of interface locations was investigated at first as the experimental settings. The results indicated that the interface location at 0.5 times the axial spacing was most suitable for the computation of rotor-stator interaction，which was closest to the experimental results of tonal noise. Then，the effect of axial spacing on tonal noise was calculated. With the decrease of axial spacing，harmonic loading on the stator vanes and sound radiation in the far field showed an increasing trend. The shape of noise directivity at the first blade passing frequency (BPF) was similar，and the noise directivity at the second BPF showed big difference in shape and amplitude.