| The vacuum tube maglev train system has become one of the important directions of future research on high-speed trains due to its low resistance and low noise characteristics.In this paper,using the SST k-ωturbulence model and large eddy simulation method,the effects of different speed levels(600-1600 km/h),blocking ratios(0.12-0.3)and vacuum degrees(0.1-0.3 atm)on the aerodynamic performance of the train are studied;The characteristics of the aerodynamic noise sources on the train surface at different speed levels are analyzed;by using the SEA model,by loading the surface aerodynamic noise excitation,the distribution law and regional contribution of the train interior noise are obtained;on this basis,the interior noise control scheme design is carried out.The main conclusions of this paper are as follows:(1)Under the conditions of a typical vacuum degree of 0.3 atm and a blocking ratio of 0.15,no shock wave appears on the maglev train at a speed of 600 km/h;a shock wave appears on the shoulder of the tail car at a speed of 800 km/h,and the range of the wake vortex reaches the maximum;Oblique shock waves appear in the wake region with train speeds of 1000 km/h and above and reflect downstream through the wall to form a reflection shock wave train.(2)The greater the speed of the maglev train,the more obvious the drag reduction effect of the high-vacuum tube.After the vacuum degree is reduced from 0.3atm to 0.1atm,the resistance of the whole train drops by73.0% at most.If the blocking ratio is too high,it will lead to serious tube congestion,and the train resistance and noise level will be affected.after the blocking ratio dropped from 0.3 to 0.12,the resistance of the whole train dropped by 74.2%.(3)The top and bottom of the head and tail car of the maglev are concentrated areas of aerodynamic excitation.When the train speed is increased from 600 km/h to 800 km/h,the energy ratio of the surface sound source of the head car significantly exceeds that of the tail car,and the energy contribution of the surface sound source tends to shift from the lower part of the car body to the upper part.The sound energy spectrum in the upper part of the car body is shifted to high frequencies,and the lower part of the car body is biased towards low frequencies.The interaction between the shock wave and the boundary layer inhibits the formation of large-scale vortices,and the variation of vortices tends to form small-scale vortices with high frequency and high intensity.(4)The noise distribution trend of the maglev train is that the head and tail cars are larger,and the middle car is smaller,and the tail car is slightly larger than the head car.The noise at the top of the car is generally lower than at the bottom.As the speed increases,the shift of the interior noise from low frequency to high frequency becomes more pronounced.The contribution rate of the interior noise at different speed levels is dominated by the medium and low frequency noise of the floor and the medium and high frequency noise of the tail end.(5)The noise control in the maglev train is carried out through three methods of sound insulation,sound absorption and vibration reduction,and a comprehensive control scheme combining the three is proposed.The greater the thickness and density of the noise reduction material,the better the sound insulation effect.After the three methods are comprehensively processed,the reductions of the in-vehicle sound pressure levels in different areas of the 600 km/h and 1000 km/h trains are 7.00-9.62 dBA and 9.48-12.90 dBA,respectively. |
