Test And Simulation Study On Air Braking System Features Of Freight Trains

With the rapid development of China's economy,the demand for heavy haul freight trains is increasing.Due to the large inertia of heavy haul freight train,the driver's braking operation becomes complicated,and the longitudinal impulse force produced in the braking process may cause serious accidents.Therefore,it is of great significance to study the air braking features of heavy haul trains for railway freight transportation to enhance transport capacity and operational safety.The air brake system of heavy haul trains is a complex pneumatic system,and its transient working features can not be solved directly.The simulation model of the air brake system of the vehicle is established based on the test rig and aerodynamic.Analyze the transient pressure characteristics of the braking system using the data-driven simulation model,and the correctness of the simulation model is verified by comparing with the experimental data.The main contents of this paper are as follows:Firstly,according to the theory of air braking,the flow process of gas in the train air braking system is analyzed.The analysis results show that the system can be calculated according to the ideal gas isothermal process.And the calculation method of key parameters such as friction coefficient of flow in pipe is analyzed,which provides a theoretical basis for the establishment of simulation model and the selection of parameters.Secondly,a complete data acquisition and analysis system is developed on the basis of the 120 valve air brake test rig,which realizes the synchronous data collecting based on network time protocol and distributed sampling system,and analyses the transient response features of control commands and system state data.The state data is acquired based on synchronous data collecting,and then the data is correlated with the control instruction according to the the time stamp of both,so that the dynamic response characteristics of the braking system pressure are obtained after the braking command is applied.Thirdly,the simulation model of single vehicle braking system is built based on AMESim simulation platform,the 120 valve,empty and load adjusting valve,braking pipe and braking cylinder are analyzed in detail.The working principle and dynamic pressure features of each sub-model are validated by using test test rig data to driving the simulation model.The dynamic pressure features of the brake cylinder during braking and release are obtained by simulating and analyzing the brake system under different stroke of the brake cylinder and different conditions of empty and heavy vehicles.The calculated results are in good agreement with the theoretical analysis results and the data analysis of test rig.Finally,the simulation model of braking system of marshalling train is established,and the simulation analysis of inflating characteristics,common braking and emergency braking characteristics of marshalling train brake system is carried out,and the results are compared with the data analysis of test rig.The analysis results show that the simulation model can well simulates the working features of the braking system in the train.The simulation calculation of the braking wave velocity and the release wave is in good agreement with the test rig experimental results.The propagation law of the braking wave along the train pipe is consistent with the test rig experimental results.