Research On Noise Reduction Of Electric Locomotive Recooling Device

Electric locomotive has become an important carrier of railway construction in China because of its advantages of large power,high speed and high energy utilization.During the operation of electric locomotive,the equipment on board will generate huge heat,which must be ventilated and cooled by the ventilation and cooling system,and the recooling device is one of the most important ventilation and cooling systems.However,the noise generated by fan rotation and air flow in the recooling device will radiate out with the air flow,making the inlet and exhaust noise become a major noise source in addition to wheel and rail noise,and aggravating the noise pollution along the railway.Especially when the train stops on the platform,the noise from the air intake becomes the main noise source of the platform noise.Therefore,the study of aerodynamic noise of recooling unit has important social significance and industrial application value.Based on certain electric locomotive cooling tower as the research object,using flow field analysis software,the flow field of cooling tower model is established,the calculation and analysis for the steady flow field characteristics,in the steady state flow field calculation results for the initial value,the calculation and the transient flow field characteristics are analyzed,the results of transient transformation to the frequency domain,as a cooling source,using the method of numerical calculation,The sound source,spatial distribution and spectrum characteristics are analyzed.The simulation results show that: in the leading edge position of axial flow fan blade,due to the huge pressure difference between suction surface and pressure surface,leakage flow occurs at the leading edge of blade and blade tip,resulting in vortex,forming a dipole source,which is the main noise source of cooling tower and also the source of vortex generation.There are obvious eddy currents at the exit of impeller,the back of motor and the section mutation.The blade near the top has irregular low amplitude velocity pulsation,and the velocity pulsation in the middle of the blade becomes periodic,which will affect the spectral characteristics of its radiated noise.The surface source intensity reaches the maximum when the first-order blade passes through the frequency,and the noise radiated from it to the inlet and outlet is dominated by the passing frequency noise of the first-order blade below 1000 Hz,and the broadband noise is dominated by the passing frequency noise of the first-order blade above1000 Hz.The distribution of sound field in the cooling tower is greatly affected by the boundary.The inlet and outlet are mainly affected by the sound field inside the cooling tower.Outside the cooling tower,the inlet and outlet are mainly radiated and the sound field formed by diffraction.Lay 70 mm thick glass wool board at the transition air duct and lower air duct of the cooling tower for simulation calculation,in which the total sound pressure level of the air inlet measurement point drops by 2.38 d B(A),and the air outlet measurement point drops by5.13 d B(A).The interval is better for noise reduction on the side of the air outlet.