Noise Analysis And Noise Reduction Research On Switching Valve Of Main Circuit Breaker For EMU

The noise of EMUs directly affects the ride comfort of passengers,and has been concerned at home and abroad in recent years.Among them,the noise of the switching valve of the main circuit breaker is high and frequently generated,and it is necessary to study and control it.This thesis conducts a systematic and comprehensive study on the noise of the switching valve.The research includes the causes and characteristics of the noise,the main influencing factors of the noise and the control methods of the noise.In the process,the methods of theoretical analysis,numerical simulation and experiment are comprehensively used to ensure reliable results.First,the causes and characteristics of the noise of the switching valve are studied.In this thesis,a noise test method for switching valve is proposed,and the test proves that the noise of switching valve includes impact noise and jet noise.Among them,the cause of the impact noise is the vibration of the switching valve caused by the impact of the valve core on the valve body,and the noise value is as high as 99 d B.The cause of the jet noise is that the compressed air is discharged from the exhaust port of the switching valve,and the noise value is as high as 96 d B.For in-depth research,this thesis establishes a numerical simulation model of switching valve noise,and compares it with the experimental results to verify the accuracy.The simulation results show that the impact noise has obvious directionality,the jet noise is concentrated in the conical area downstream of the nozzle with the jet axis as the centerline.The jet noise has a wide frequency range,and the spectral curve shows a saddle shape.Secondly,the main influencing factors of the switching valve noise are studied.In this thesis,the noise simulation model of the switching valve is used to study the specific effects of different factors on the noise of the switching valve.On the one hand,the influence of impact speed and valve gasket material on impact noise is studied.The simulation results show that the impact noise of the switching valve is proportional to the impact speed,and the rubber material has a good cushioning and damping effect,which can effectively reduce the impact noise.On the other hand,the influence of nozzle structure on jet noise is studied.The simulation results show that,compared with the circular straight nozzle,the special shape of the exhaust port of the switching valve weakens the jet strength and reduces the jet noise.Finally,the control methods of switching valve noise are studied.Based on the results of the causes,characteristics and main influencing factors of the noise of the switching valve,this thesis formulates the noise reduction schemes for the impact noise and the jet noise respectively.For impact noise,use damping materials for noise reduction,including rubber mats and vibration-isolating patches.Tests have shown that the noise reduction effect of up to 14 d B can be achieved.For jet noise,use mufflers for noise reduction.In this thesis,not only four kinds of industrial mufflers are selected,but also a new structure of the switching valve exhaust muffler is designed according to the jet noise characteristics.The test proves that the noise reduction effect of 20 d B can be achieved.