Study On Train Dynamic Performance And Cross-wind Safety In Snow And Ice Environment

In the northern alpine region,the EMU will experience low temperature,rain and snow in winter,and extreme natural conditions such as freezing in severe cases,which will bring a series of special problems to the operation of the alpine EMU in China.Among them,the most serious is when there is snow and ice in the bogie suspension elements,it will change the dynamic performance of the original suspension elements,so that the alpine EMU operation is faced with serious dynamic problems,endangering the safety of train operation.Therefore,in this thesis,the train dynamics models of snow and icing in the bogie area under the ice and snow environment are established respectively,and the dynamic performance of the train considering the random distribution of ice and snow mass,different freezing states,and freezing degrees are studied.Finally,this thesis also studies the safety of high-speed train operation under the condition of snow and ice in the cross-wind environment and provides reference suggestions for the safe operation of alpine EMU.Firstly,a train dynamics model with the random distribution of snow and ice mass of the bogie is established considering the mass of ice and snow,the position of the center of gravity,and the moment of inertia.The influence law of train speed grade,rail surface friction coefficient,and wheel-rail matching relationship on the dynamic performance of the train in the alpine environment is studied,and the influence degree of the random distribution parameters of ice and snow mass on the dynamic performance is explored.The results show that at the speed of 400 km/h,the random distribution of snow and ice mass does not make the dynamic performance indexes exceed the limits.With the increase of friction coefficient,the dynamic performance index decreases gradually,and increasing the friction coefficient of the rail surface can improve the dynamic performance of the train.According to the analysis,the mass of ice and snow attached to the frame directly affects the derailment coefficient and the lateral force of the wheel shaft.The ice and snow mass on the axle box has the greatest correlation to the wheel load reduction rate.The mass distribution of snow and ice attached to the motor is the main factor affecting the smoothness of train operation.Secondly,based on the nonlinear stick-slip characteristics between ice and suspension components,the train dynamics model in the snow and ice environment is established.The effects of four different freezing states on train dynamics is studied by simulation,and the effects of suspension component icing stiffness on train dynamics is explored.The results show that when a suspension or motor spring is frozen,the dynamic performance indexes of the train can meet the requirements at the speed of 400 km/h.However,when the secondary suspension or all suspension is frozen,the dynamic performance of the train deteriorates obviously,especially the hunting stability and running smoothness.When the speed is greater than 150 km/h,the train may snake instability,so it is necessary to slow down to 150 km/h to run safely.According to the analysis,freezing of the secondary suspension elements is the main factor affecting the dynamic performance of the train,especially when the anti-snake shock absorber and the secondary air spring are frozen,it is necessary to clean the ice on the secondary suspension elements in time,and cooperate with them to reduce the speed of the train.Then,the influence law of different freezing degrees on the dynamic performance of the train is studied,and the influence law of freezing stiffness of anti-snake shock absorber and secondary air spring on train dynamic performance is explored.The simulation results show that when the speed is greater than or equal to 300km/h,no matter how much ice is frozen on the suspension element,it cannot meet the requirements of safe operation in snow and ice environment,so it is necessary to deice the suspension element.When the speed is less than or equal to 150 km/h,the train can run safely in snow and ice environment.When the speed is between 150 and 300 km/h,when the freezing degree exceeds 60%,it is necessary to deice the suspension components in the bogie area of the train.Among them,the maximum icing thickness of the primary steel spring,the primary vertical shock absorber,the secondary air spring,the secondary vertical shock absorber,the anti-snake shock absorber,and the motor leaf spring when frozen at 60% can be taken as 19 mm,16 mm,21 mm,16 mm,17 mm and15 mm respectively.The safe running speed of the second-series suspension train after deicing can reach 350 km/h,which is better than the speed limit of 150 km/h before de-icing.Finally,the aerodynamic force and torque of high-speed EMU under different cross-wind speeds and speeds are obtained through aerodynamic simulation calculation,and the aerodynamic force and torque of the head car are loaded into the train dynamics model,and the train operation safety under cross-wind conditions is simulated and analyzed under snow and ice in the bogie area.The results show that when the wind speed is less than 20 m/s,the train can safely run at the speed of more than 250 km/h.When the wind speed is greater than20 m/s,the safe speed of train operation in snow and ice environment is less than or equal to100 km/h.Therefore,in a high wind environment,the freezing of the suspension elements is very unfavorable for the safe operation of the alpine EMU.