Flow Field And Thermal Analysis Of Hydraulic Shock Absorber For Railway Vehicle

The shock absorber is an important element of suspension system,during the operation of vehicle,vibration brings oil flow in working cylinder and storage cylinder of shock absorber.Chocking effects emerge by the internal valve with oil,converting vibration Energy into hydraulic heat.The temperature of the oil is rising,the heat conducts by the oil and cylinder body,distributes into the air circumstance.If the temperature is too high,the damping and sealing performance will be faced with degradation which leads to the failure.Therefore,the temperature and safety of the shock absorber have an important relation.With the development of computational fluid dynamics,based on the FLUENT simulating software and combined with the shock absorber bench test,the processes of the rising temperature,the state of thermal equilibrium temperature and the temperature-damping force influences are studied in this paper.Firstly,the fundamental structure and operating principles are introduced in this thesis,the working characteristics are analyzed.According to the thermodynamics theory,the mathematical model is deduced,qualitative analysis shows the ability of heat dissipation performance of the shock absorber.Next,based on ICEM-CFD,different speed working operating grid models are established.Based on FLUENT,gains the speed-pressure pattern by solving the grid model of the absorber under the velocity boundary condition(1 meter per second).The velocity and pressure field characteristics of different regions are analyzed under this condition.For continuous working condition with maximum speed of 0.06 meter per second,based on the dynamic grid model module and UDF(User Define Function)module,the control program of moving boundary and the valve control program are imported into FLUENT.By simulating the opening and closing of the compensating valve and the periodic motion of the piston,the transient temperature rising state and the thermal equilibrium temperature of the shock absorber are obtained,and the temperature field of the shock absorber is studied.According to the technical conditions of locomotive oil hydraulic shock absorber,the heat-balanced temperature test is carried out on the test bench under three working conditions,and the test results are compared with the simulation results under the same working conditions(0.06 meter per second).Finally,according to the heat-balanced temperature test,the influences between the temperature of the shock absorber and its damping performance are studied.The results show that the flow field of the three flow holes of the shock absorber is similar under the velocity working condition(1 meter per second),which reflect that the structural characteristics of the three restoring valves are comparatively consistent,this results ensure the normal operation of the shock absorber.Under the continuous working condition with maximum speed of 0.06 meter per second,the thermal equilibrium temperature is positively correlated with the motion speed of the shock absorber,and the simulating results are in good agreement with the test results.The oil temperature of the shock absorber increases,and the damping performance of the shock absorber decreases.