Effects Of Surface Dielectric Barrier Discharge On Aerodynamic Characteristic Of Train

At present,the high-speed train has become one of the indispensable means of transport due to the large passenger carrying capacity,high punctuality,good safety and environmental protection.However,with the continuous increase of the train speed,the fluid-solid coupling problem of the train is increasingly prominent and the further speed-raising of the train is inhibited because the air-resistance of the train increases quadratically with the service speed of the train.At the same time,with the increase of train aerodynamic drag,the positive pressure between the train wheel and the rail reduces because its vertical component(aerodynamic lift)is also proportional to the square of the speed,reducing train maneuverability,safety,and deterioration of passenger ride comfort.Therefore,in order to ensure the safe operation of the train and achieve the goal of "energy saving,environmental protection and noise reduction",it is necessary to study the optimization of the aerodynamic characteristics of the train.In order to reduce the air resistance of the train,the main work is to streamline the geometry of the train head and to streamline the cross-sectional shape of the vehicle body.However,this method needs to be fitted with the actual working conditions and has certain limitations.Nowadays,the plasma active flow control technology can reduce or suppress the boundary layer separation and turbulence transition by inputting local energy to reduce the train pressure resistance.Therefore,this paper studies the optimization of the aerodynamic characteristics of the train by the surface dielectric barrier discharge plasma actuator.In this paper,aiming at the self-discharge characteristics of the surface dielectric barrier discharge actuator,a plasma test system was set up to analyze the discharge mechanism from the aspects of electrical characteristics and optical characteristics.In order to optimize the aerodynamic characteristics of the train by surface dielectric barrier discharge device,this paper presents the variations of some key parameters such as plasma extension,discharge voltage,discharge current,power consumption,temperature field distribution,body force and induced flow with different electrode gap and structure.The influence of discharge structure on the dielectric barrier discharge characteristics was elucidated by the equivalent circuit.Based on the research of the surface dielectric barrier discharge actuator and wind tunnel simulation experiments,this plasma actuator was applied to the head and tail of the train model respectively,the air field around the train model was visualized by the smoke visualization experiment.The mechanism of the plasma actuator in optimizing the aerodynamic characteristics of the train was revealed and the effect of the applied voltage and the electrode structure on improving the train flow separation and reducing the train air resistance was comparatively studied,which will provide some guidance for optimizing the aerodynamic characteristics of the train and achieving further speed-raising.