Simulation Analysis of Jet Noise from High-speed Railway EMU Main Circuit Breaker Switching Valve and Noise Reduction Measures

Objective The jet noise generated by the main circuit breaker switching valve of high-speed railway EMU is excessively high, which seriously affects passenger comfort. Therefore, it is essential to study effective noise reduction measures. Method Field experiments are conducted to measure the jet noise of the switching valve, revealing a noise level as high as 96 dB with noticeable intermittency and pulsation. Using LES (large eddy simulation), a mathematical model for simulating the jet noise of the switching valve is established. Four different nozzle shapes are selected, and their flow velocity distribution nephograms are computed. The calculated jet flow results are imported into LMS.Virtual.Lab software, and the acoustic boundary element method is employed to simulate the jet noise fields of the four nozzles. The simulated 1/3-octave frequency spectrum values for them are compared with experimentally measured values. Finally, four existing industrial mufflers and a developed new structural composite material muffler are selected and tested for their noise reduction effectiveness on the switching valve. Result & Conclusion Generated by main circuit breaker disconnection, the jet noise of the switching valve is closely related to the shape of the exhaust port and falls into the mid-to-high-frequency noise range. All five mufflers can significantly reduce the jet noise from the switching valve, with the new structural composite material muffler demonstrating the best noise reduction effect, achieving a reduction of up to 20 dB.