Research And Optimization On The Aerodynamic Characteristics Of High-Speed Train Pantograph Under Crosswind

Pantograph mounted on the top of high-speed-train is composed by many different parts in complicated shape. Three dimensional viscous flow filed around the pantograph is complex and strongly nonlinear when the train running. However, the flow field and aerodynamic performance of pantograph will be changed when it running in cross wind, and the stability of pantograph on operation and the quality of absorption current will be also influenced. There has been a substantial amount of research carried out to investigate the effects of cross wind on high-speed-train pantograph and the aerodynamic characteristics both at home and abroad at present. However, further research is need on complicated scene modeling, crosswind aerodynamic force and moment analysis, unsteady properties of crosswind and the flow characteristics of the circular cylinder similar as pantograph.The SSS400+pantograph, CRH high-speed train and actual catenary are taken as research models while theoretic analysis, model test and numerical simulation were applied compositely. Aerodynamics of high-speed-train pantograph under crosswind, aerodynamics of the cone components in pantograph and cylinder bar, and the lift force of pantograph in crosswind were simulated. The main contents are as follow.1. Influence of complicated scene modeling on aerodynamic characteristics of pantograph in cross wind was studied. Results show that the difference of aerodynamic force and moment between pantograph model and pantograph-catenary model is less than5%. The difference of aerodynamic force and moment between pantograph-train model and pantograph-catenary-train model is less than7%. The difference of aerodynamic force and moment between pantograph-catenary model and pantograph-catenary-train model is13.8%～65.2%, so the train should not be neglected. Relationship of aerodynamic force and moment coefficient of pantograph and train speed, crosswind speed and direction was established.2. Detached Eddy Simulation(DES) method was applied to simulate the unsteady external flow field around pantograph and its main parts under crosswind condition. Difference of aerodynamics between pantograph in open operation and close operation were examined. Result show that the flow field around pantograph is obviously influenced by the pantograph dome on the top of train, the train junction and catenary model. Flow field characteristics were changed to some extent. The external flow field flow field characteristics of front slide plate and back slide plate is obvious different. Lift force coefficient and pitching moment coefficient of upper and lower arm links is affected evidently by complex wake vortex structure. The mean of aerodynamic force coefficient and moment coefficient of pantograph in open operation is larger than in close operation, so as the frequency domain range of the corresponding amplitude. Vibration in horizontal direction is increased in open operation.3. Large Eddy Simulation(LES) method was applied to simulate characteristics of circular cylinder, variable cross-section circular cylinder and pantograph cylinder of different sizes. For the circular cylinder, relationship between drag coefficient, Re and aspect ratio (L/D) was established. For the variable cross-section circular cylinder, relationship between drag coefficient, Re, aspect ratio (L/D) and θ (angle between side bus and axis) was established. The influence of the end face in variable cross-section circular cylinder to the drag coefficient was also revealed.4. Optimization study on aerodynamic configuration was applied to slide plate, upper and lower arm links under cross wind. Simulation with DES method was applied to inspect the effect of the optimization on the pantograph. The results show that wave circular cylinder is better in drag reduction and vibration absorption under small angle of attack, whose surface structure had strong control to flow field. Better aerodynamic performance of slide plate was achieved after the optimization to the cross-section. Also by rise the baffle on each side of pantograph, better aerodynamic stability is achieved under strong crosswind. Pantograph with single arm slide plate performed excellently under500km/h speed.5. Transfer coefficient between aerodynamic force and aerodynamic uplift force of pantograph and main parts under cross wind was obtained by analysis to geometric relation and force of main parts of high-speed-train pantograph. Results show that lift force of pantograph distributes mainly on collector head. The lift force of upper frame is always negative while the absolute value of lift force of lower arm is smaller. The relationship between aerodynamic force of pantograph and the variables of train speed, crosswind speed and direction are described by formulas.