Experimental Study On Influence Of Exhaust From High Speed Train Equipment Cabin On Boundary Layer Characteristics Of Downstream Car Body

During the increasing of the train speed,a large amount of heat will be generated in the equipment cabin at the bottom of the compartments,the problem of ventilation and heat dissipation in the equipment cabin will be increasingly significant.When the train runs at the high speed,airflow outside the compartments flows relative to the opposite direction of the train very fast.Through the air vents of the equipment cabin,the ambient airflow as the cooling medium is sucked into equipment cabin,compared with the relative movement speed,the airflow is sucked/injected at a lower speed at the vent,the formation of a weak suction/injection flow phenomenon.However,the suction/injection phenomenon that occurs when the high-velocity airflow passes through the air vents of the equipment cabin will cause the changes in the structure of the flow field near the wall surface of the downstream car body,which will create a lateral force that will affect the operational safety of the train.Therefore,the design of high-speed trains has to consider the effect of equipment cabin ventilation on the downstream car body boundary layer characteristics.This article mainly uses the experimental method to study the influence of the injection phenomenon in the exhaust vent of high-speed train equipment compartment on the flow field structure near the wall surface of the downstream body.The experiment is based on the L-type standard Pitot tube mounted on a three-dimensional coordinate frame testing mechanism to obtain flow field information in the vicinity of the air vents and on the downstream cross section.Through the analysis of experimental data,the following conclusions are drawn:(1)The velocity of the air flow simulating the speed of the train has little influence on the injection velocity,and the injection velocity is 2.94 m/s,on this basis,the velocity difference does not exceed 1 m/s.(2)When the flow velocity is equal on both sides of the suction air duct and the injection air duct,the average velocity at the cross section x=-1190 mm upstream of the injection air duct is 35.72 m/s,and the average velocity at the downstream x=4825 mm cross section is 41.38 m/s.Flow velocity increases,indicating that the injection velocity affects the structure of the injection duct flow field downstream,and the injection velocity is 1.59 m/s.(3)Within all measured cross-sections,in the direction perpendicular to the wall surface of the car body,in the range of y=35 mm to y=125 mm,the trend of the inflow velocity at the measuring point in the corresponding position is uniform as a whole.The flow velocity increases first and then decreases.At z =68 mm,the flow velocity is the highest,and the velocity of the incoming flow near the wall y=5 mm is smaller than the velocity at the other side near the wall y=155 mm.(4)The flow velocity in the direction of the plumb bob increases first and then decreases,and the change in flow velocity near the wall z = 98 mm decreases first and then increases along the flow direction,and the amount of change in speed not far from the downstream area of the exhaust vent is the smallest.(5)Overall,the variation of the incoming flow velocity gradually decreases from the upstream to the downstream of the jet air duct along the incoming flow direction.