Aerodynamic Noise Investigation of Metro Vehicle Auxiliary Converter

To solve the problem of a 1.5 dB (A) noise excess in a metro vehicle auxiliary converter, the aerodynamic noise characteristics of an auxiliary converter are investigated by combining a numerical simulation with a noise test. First, the noise from aerodynamic sources in the auxiliary converter was calculated using a large eddy simulation. Then, the sound propagation of aerodynamic sources of noise through ducts and surrounding spaces was calculated, based on an acoustic analogy method. Finally, the vortex and noise distribution contours in the fan and duct area were analysed, and trends in the simulation and test results of the sound pressure level spectrum at the test points were compared. The results indicate that at a distance of 0.4 m from the outlet, the peak frequency is 290 Hz under both conditions, and there is a 5% difference in amplitude. This demonstrates that the simulation method is correct and feasible. The vortex and noise distribution contours in the fan and duct area indicate that the inhomogeneity of air velocity at the fan inlet, and the significant vortex in the vicinity of the blade, are major contributions to the primary noise source, which is around the fan. By adding a thin, square-shaped honeycomb in front of the fan inlet, the velocity is rendered more uniform, and the overall sound pressure level is reduced by approximately 2.5 dB (A) at the test point.