Research On Characteristics And Control Of Aerodynamic Noise Generated By An EMU Traction Transformer Cooling Fan

Traction transformer is one of the nine key technologies of high-speed EMUs,its heat dissipation performance plays an important role to driving safety.Cooling fan,as one kind of cooling equipment,is widely used in high-speed EMUs nowadays.However,it also introduces a relatively significant aerodynamic noise problem,and becomes one of the main sound sources of the undercarriage of EMUs.Therefore,it's of great significant to study the characteristics and control of aerodynamic noise generated by an EMU traction transformer cooling fan.In this paper,research on the characteristics and control of aerodynamic noise caused by a certain type of cooling fan of EMU traction transformer are studied combined with test and simulation tools.The main research works are listed as follows:Firstly,the aerodynamic noise test of the cooling fan has been implemented according to the fan noise measurement standard.Based on the test data,the aerodynamic noise characteristics of the fan are analyzed to clarify the main noise frequency band and order noise.At the same time,the specific A-weighted sound level,the contribution rate of the order noise and broadband noise,the radiated sound power are calculated based on these data.Results show that the aerodynamic noise level of the air inlet and outlet measuring points are the most significant;the specific A-weighted sound level of the air outlet measuring point is the largest;the contribution rate of broadband noise is much higher than order noise;the radiated sound power of the fan is about 105 dB.Secondly,a simulation model is established based on the three-dimensional geometric model,with consideration of the actual structure of the motor and the bracket.Based on the computational fluid dynamics and the Lighthill acoustic comparison theory,the unsteady flow characteristics of the cooling fan and the far-field sound field are numerically simulated to explore the noise's mechanism and identify the main noise sources.At the same time,the validity of the model is verified with the test data,which provides a reference model for the following work.Finally,three aerodynamic noise control design schemes are proposed based on the test data and simulation analysis.Based on the verified simulation model stated above,simulation calculations of these schemes are made.According to the simulation results,the optimal noise control scheme is selected.Then the prototype fan of this scheme is developed and the aerodynamic noise test is made again.The test results show that the total sound pressure level of the prototype fan is about 7.4 dBA lower than that of the original one.The results of the characteristics and control scheme design of aerodynamic noise of the high-speed EMU traction transformer cooling fan obtained in this paper can provide a practical reference for the improvement of the aerodynamic performance of the cooling fan.