Research On The Aeroelasticity Of Pantograph-iced Catenary System Under Cross Winds

In order to provide traction power for high speed trains,electric locomotives collect current from overhead catenaries by pantographs which are mounted on top of the car body.In the progress of running,disturbance between pantograph strips and the contact wire can cause the vertical vibration of pantograph-catenary coupling system,which may affect the current collecting quality.With the rapid development of railway transportation in our country,the high speed railway coverage has become wider and wider.Correspondingly,the operation environment of high speed trains has become more complicated.It's worth noting that for areas of low temperature and high humidity and altitude,it is likely for catenary to be covered with ice.Under the action of cross winds,dancing phenomenon would occur for the iced catenary,which can affect the dynamic characteristics of pantograph-catenary system,or even cause train withdrawn and severe equipment damage.Therefore,it is theoretically and practically worthy to study the dancing mechanism of the iced catenary.In this dissertation,a vertical pantograph-catenary dynamic model and a dancing model of multi-dimensional iced catenary is proposed.By analytical and numerical methods,aeroelasticity of iced catenary and pantograph and their influence on the dynamic characteristics of the pantograph-catenary system are discussed in detail.The main contents and achievements are as follows:Firstly,a simple catenary and lumped mass model pantograph coupling dynamic system is built.In the model,displacement compatibility equations are introduced to feature the contact relation between pantograph strips and the contact wire.In the meantime,Coulomb model is applied to present the friction force between pantograph and catenary,and the transfer coefficient method is used to obtain the equivalent lift force from the friction force.By comparing to the reference model in the European Standard EN50318,the vertical dynamic model of pantograph-catenary coupling system is proved to be valid.On this basis,under different running conditions of pantograph(opening stomata or closing stomata),the influences of frictional force on the dynamic performances of pantograph-catenary interaction are discussed.Besides,the changing laws of the statistics of contact force with friction coefficient and pantograph rising angle are provided.Secondly,aiming at the dancing phenomenon of iced catenary under cross winds,the vertical dancing model of iced catenary is established.By CFD simulation of the iced contact wire under cross wind,the aerodynamic coefficients of different angles of attack are obtained.Based on the quasi-steady theory,the expression of vertical aerodynamic force of iced contact wire is derived and generalized to the dancing model of iced messenger wire.According to the Den-Hartog vertical galloping criterion,the necessary condition for the aero instability of iced catenary is determined.Moreover,the varying parameter analysis is carried out to study the influence of wind velocity,initial angle of attack and structural damping on the galloping oscillation.Results show that the primary cause for the galloping oscillation of iced catenary under cross winds is the aero instability.Besides,increasing of the structural damping can raise the critical condition of instability,which can control the occurrence of the vertical dancing of the iced catenary.After the preliminary investigation of vertical galloping mechanism of iced catenary,the aerodynamic forces on the running pantograph under cross wind are simulated by CFD,the dynamic characteristics of pantograph-catenary system under cross winds are studied.By the numerical calculation,it is found that cross wind on the pantograph can cause the mean value and standard deviation of contact force to grow obviously,on the iced catenary can cause the pantograph head displacement and the uplift at support to increase.Both of them would reduce the safety and stability of current collecting.At last,considering the different galloping initiation mechanism,such as torsional and inertial coupling mechanism,and the large deformation during galloping vibration of iced catenary,based on the Euler-Bernoulli beam theory and Hamilton principle,a multi-dimensional dynamic model of iced catenary which can describe the geometric nonlinearity caused by large deformation is established.In addition,the expressions of vertical and lateral elastic forces of droppers and supports,as well as the expressions of multi-dimensional quasi-steady aerodynamic forces are given.On this basis,the stability and response analysis of vertical-lateral coupling and vertical-lateral-torsional coupling iced catenary model are carried out.Results concluded from the stability analysis are that for the vertical-lateral model,in the initial angle of attack parameter plane,the instability region is relatively small while the corresponding critical wind speed is low.For the vertical-lateral-torsional model,the area of instability region is large while the critical wind speed corresponding to the enlarged region is high.Results from the response analysis are that the 1:1 internal resonance may occur during the galloping of the both type of iced catenary models.When the 1:1 internal resonance takes place,the galloping amplitude would increase sharply.In the nonresonance region,the galloping amplitude is relatively small.Furthermore,by comparing galloping responses of the vertical-lateral-torsional model with and without geometric nonlinearity,the fact that the 1:1 internal resonance is caused by the geometric nonlinearity is proved.In general,researches above have revealed the mechanical mechanism of the galloping oscillation of iced catenary under cross wind and the aeroelastic response of the pantograph-catenary coupling system,which can provide some particular theoretical basis and suggestions for the future optimization design work and vibration control of the system.