A Study On The Low-temperature Damping Characteristics Of A High-speed Train Hydraulic Damper

Hydraulic dampers are key components in modern railway vehicle suspensions,which play important roles in safety,comfort and stability of the train.That conducting research work on the low-temperature damping characteristics of the hydraulic damper is of great significance to both improve its environmental adaptability and dynamic performance of the train operating in extreme cold weather conditions.In this study,physical properties of damper fluids are investigated experimentally and theoretically in a wide temperature range,a theoretical density-temperature model and an improved viscosity-temperature model based on the Vogel formula are proposed to describe the physical properties of the fluids in a wide temperature range,the proposed formulae overcome shortcomings of existing models which are only suitable for normal temperature conditions,and thus make the current physical property models are more suitable for a wide temperature range and more accurate.In order to carry out experiments on low-temperature fluid mechanics of hydraulic orifices,this study changes the existing experimental principle which is under room temperature conditions,and proposes an integrated experimental module which integrates the oil,the oil supply mechanism,the test valve with orifice and several sensors.The experimental module can be wholly placed into a high/low temperature chamber to undertake experiments.Based on the integrated experimental module and virtual instrument technology,a novel experimental apparatus,which is capable of carrying out fluid mechanics experiments automatically on hydraulic orifices under low or high temperature conditions,is developed.By using the developed experimental apparatus,experiments on fluid mechanics of common hydraulic orifices are carried out in a wide temperature range of-50 ℃ ～ + 80 ℃,Flow-pressure curves and Discharge coefficients of the hydraulic orifices under different temperature conditions are obtained.Combined with the proposed theoretical formulae for describing physical properties of damper fluid in a wide temperature range,the effects of temperature,especially low temperature,on Flow-pressure characteristics,Discharge coefficients and damping forces of sharp-edged and thick-walled orifices are investogated;Based on the obtained basic theory and experimental data of low-temperature fluid mechanics of hydraulic orifices,combining with the testing results of low-temperature damping characteristics of high-speed train hydraulic damper,the distortion mechanism of the Force-displacement curve of the damper under low-temperature conditions is analyzed,the variations and features of key technical indices of the damper,such as maximum damping force,absorption work,dynamic damping rate and dynamic stiffness,are analyzed.The obtained results provide a basis for further hydraulic damper design optimization and improvement of its low temperature adaptability.Research results of this thesis have brought a core experimental platform and the basic theory for further research and optimization of hydraulic components and high-end equipments,including high-speed train hydraulic dampers,which are required to serve in severe environments.