Research And Application Of Influence Of Train Pipe Pressure Gradient On Heavy Haul Train

With the development of heavy haul transportation technology in China,the traction weight and configuration length of heavy haul trains continue to increase.At the same time,it also brings some safety problems,such as: the increase of transmission time of train braking wave and release wave leads to excessive longitudinal impulse.When the train is released,it takes a long time to recharge,which leads to a large difference in the braking force of the train when the train pipe does not reach the specified pressure.It is difficult for the driver to accurately judge the braking force of the train,which in turn makes it difficult to control the speed of the train.It is necessary to take measures such as additional train pipe pressure reduction to stop the train.Restricted by of line conditions and the continuity and periodicity of train operation,it is limited to reduce the longitudinal impulse by optimizing operation.These problems seriously affect the safety and efficiency of train transportation.Air brake system is an important source of braking force of heavy haul trains,and it is also the main factor affecting the longitudinal impulse of trains.It is of great significance to use the simulation system to study the air brake system of the train.The Train Air Brake and Longitudinal Dynamics Simulation System(TABLDSS)was used to explore the influence of train pipe pressure gradient on the braking performance,longitudinal impulse and related characteristics of 10,000 t train,20,000 t train with conventional configuration and 20,000 t train with slave locomotive moving backward,and the quantitative analysis results were obtained.The current braking force judgment standard and adjustment method of 20,000 t heavy haul train in Shuozhou-Huanghua Railway are explored,and the braking force judgment standard of heavy haul train with data support is put forward,and the improvement ideas are put forward to solve the problem of abnormal train parking.From the perspective of changing the position of the slave locomotive,the braking capacity,longitudinal impulse and recharging ability of the 20,000 t train under different configurations are explored,and the configuration of the 20,000 t train with excellent comprehensive performance is obtained.The research results show that with the increase of the reduction of the train pipe pressure,the influence of the train pipe pressure gradient on the train braking performance,longitudinal impulse and braking characteristics is reduced.In terms of braking performance,when the pressure gradient of train pipe is larger,the average value of the brake cylinder balance pressure is lower,and the braking ability of train is weaker.In terms of longitudinal impulse,the greater the pressure gradient of train pipe,the greater the compression coupler force generated during braking and the smaller the tensile coupler force during release.In terms of braking characteristics,the braking wave transmission rate of 10,000 t train increases with the increase of the initial train pipe pressure gradient,but the rising rate of brake cylinder pressure decreases.The braking wave transmission rate and the rising rate of brake cylinder pressure of 20,000 t train with conventional configuration and 20,000 t train with slave locomotive moving backward decrease with the increase of the initial train pipe pressure gradient.In terms of release characteristics,for 10,000 t trains and 20,000 t trains with conventional configuration,the greater the train pipe pressure gradient before braking,the faster the release wave transmission rate.For the 20,000 t train with slave locomotive moving backward,the transmission rate of the release wave of the rear vehicle remains unchanged,while the transmission rate of the release wave of some vehicles in the front of the train is different and shows disorder.When the air brake is used to adjust the speed in the train operation,the influence of the pressure gradient of the train pipe on the braking performance of the train cannot be ignored.The tail pressure of the train pipe can be used as one of the factors to judge the braking force of the train.The different positions of locomotives in the train will greatly affect the braking capacity,coupler force and recharging performance of the train;when the slave locomotive is located around 2/3 of the train,the comprehensive performance of 20,000 t train is excellent.The simulation results in this paper are of great significance to ensure the transportation efficiency and operation safety,and to develop the automatic train driving technology.