Research On Unsteady Aerodynamic Characteristics Of High-speed Pantograph

With increasing the train speed,strong air disturbance and pantograph-catenary coupling vibration are exerting greater effects on the sliding contact characteristics of pantograph and centenary.The drag force of the pantograph accounts for 7%-14% of the total vehicle drag force.The high-speed airflow not only has negative effects on the drag reduction and noise reduction,but also causes the fluid-induced vibration of pantograph,which makes the coupling vibration of pantograph more obvious.In the paper,the aerodynamic characteristics of the pantograph will be researched.Based on the computational fluid dynamics and finite element theory,the aerodynamic model of the pantograph,the fluid-solid coupling model of the pantograph and the dynamic model of the pantograph-catenary are established to study the unsteady aerodynamic characteristics of the pantograph and the current collection of the pantograph-catenary system.Firstly,the aerodynamic model of pantograph is established and the unsteady aerodynamic forces of pantograph contact strips with different distances are simulated by the method of detached eddy simulation.The simplified model of three-dimension pantograph is established by using Solidworks.The pantograph models with different distances of contact strips are built,incuding five types: 270 mm,360mm,450 mm,540mm and 630 mm.The three-dimension pantograph model is imported into ICEM to create the flow field calculation region.The pantograph wall surface and the flow field region are meshed.The boundary layer grid is also generated.Then,the grid model is imported into Fluent to set the turbulence model,boundary conditions and solving algorithm for simulation.The aerodynamic time-domain characterisics of contact strips are analyzed.In addition,the aerodynamic power spectrum density of the contact strips are obtained by using the fast fourier transform method.The results show that with the increasing of the distance between the contact strips,the lift force of the rear contact strip changes from the negative to the positive lift force,and the fluctuation range is large.The power spectrum density of pantograph contact strips with different distances is obviously different.Secondly,the fluid-solid coupling model of pantograph is established.The aerodynamic law of pantograph is studied by comparing the fluid-solid coupling analysis and the direct flow field analysis at different velocity levels.Based on the computational fluid dynamic theory,the reynolds average navier-stokes method(RANS)is used to establish the aerodynamics model in Fluent.The simplified pantograph model consisting with the model used in aerodynamic analysis is imported into the Transient Structure to establish the dynamics model of pantograph.The fluid pressure and structural displacement data in Fluent and Transient Structure are exchanged using the System Coupling solver in Ansys Workbench to obtain the pantograph aerodynamic force considering the fluid-solid coupling effect.The uplift force of the pantograph is obtained by calculating the aerodynamic equivalent of each part of the pantograph.The results show that the uplift force of the pantograph increases under fluid-solid coupling analysis.With the increase of running speed,the effects of fluid-solid coupling on the aerodynamic force of the pantograph components and the uplift force of the pantograph are gradually significant.Finally,the pantograph-catenary dynamic model is established by using the lumped mass model of pantograph and the finite element model of caterary.The uplift force of pantograph considering the fluid-solid coupling effect is loaded into the pantograph-catenary dynamic model,and the influence of fluid-solid coupling aerodynamic force of pantograph on pantograph-catenary dynamics is analyzed.The results show that the mean value,maximum value,minimum value and standard deviation of contact force increase under the fluid-solid coupling analysis.