Experimental and Simulation Analysis for Aerodynamic Noise of an EMU Traction Transformer Cooling Fan

In order to study the aerodynamic noise characteristics of EMU traction transformer cooling fans, aerodynamic noise test is carried out for a certain type of cooling fan, and the sound pressure level and spectrum characteristics at different measuring points are obtained. At the same time, a simulation model is established for this type of fan. In the model, the motor, support and other fine structures are considered. Combined with the computational fluid dynamics method and Lighthill acoustic comparison theory, the unsteady flow characteristics and far-field sound field of the cooling fan are numerically simulated and compared with the test data. It can be seen that the main orders of the cooling fan noise obtained by using the large eddy simulation method are consistent with field test results, showing the effectiveness of the simulation model. Relative importance of broadband noise and rotation order noise are analyzed for the fan’s lateral evaluation point. In terms of sound pressure power spectrum density, broadband noise contributes 74.76% while rotation order noise contributes 25.24%. Thus noise reduction should be directed to broadband noise. For rotation order noise, it is found that the main sources are of dipole nature produced by airflow pulsating pressure at the inlet impeller and the outlet impeller. For orders associated with the inlet impeller, the 10th order is most important while for the outlet impeller, and the 33rd order is most outstanding. The obtained analysis results may provide a useful reference for the improvement of the aerodynamic performance and aerodynamic noise of the fan. © 2019 Journal of Mechanical Engineering.