Study On Modelling The Longitudinal Dynamics Of Heavy Haul Train

The development of heavy haul transportation has become the major direction in the railway freightage domestically and internationally. However the longitudinal impact issue stands out when the traction weight and the formation length of the trains increase which in turn aggravate the risk tendency of couplers breakdown or crush derailment. Therefore, it is of significant importance to proceed intensive study on longitudinal dynamics problems, improve the analytical models and propose guidelines for design rationality, operation safety as well as the optimization of the railway vehicle.Based upon the background illustrated above, this paper studies the longitudinal dynamics modeling method for the heavy haul train, proposes a coupler model based on the non-inertial coordinates, establishes a mathematical model for the heavy haul train air-braking system in accordance with the finite element and multi-body theory, improves the research theory and approach for railway train longitudinal dynamics problems. The main work involves:1. Establish the longitudinal dynamics model of the train with respect to the trajectory coordinate system of which the coupler force is generated by interpolating the dynamice force-displacement curve of the buffer from drop test, the brake forces under different cases are calculated from the pressure-rising curve of every brake cylinder in the train formation during brake indoor standing tests while the delay time of the brake cylinder is obtained from the horizontal section of the cooresponding curve as well. This model is applied to study the influences of the buffer performance parameters, traction tonnage and the coupler’s slack to the longitudinal impact of the train under typical working conditions.2. Propose a new three-dimensional coupler model based on the non-inertial coordinate which allows for arbitrary three-dimensional motion of the car bodies and captures kinematic degrees of freedom of coupler systems including the relative rotational displacement of the coupler against the carbody using the quasi-static equilibrium hypothesis. It does not lead to an increase in the number of longitudinal dynamical equations, number of the system inertial coordinates and number of constraint equations.3. Establish the mathematical model for the brake pipe of the train which can cover the leage and pipe wall friction, basing upon the gas dynamics and continuum mechanics theories. Obtain the pressure/speed coupled partial differential equations of the brake pipe which depend on the time and the longitudinal coordinates of the brake pipe, these equations can be solved by finite element method. Build the mathematical model of brake unit of the cars basing on the state equation of ideal gas and combine this model with the pipe’s to construct a new finite element/multi-body mathematical model for air brake system in the heavy haul train. This model is applied to simulate the brake force in the longitudinal dynamical analysis of the railway train.4. Build the longitudinal dynamical model under trajectory coordinates for the20,000tonnage heavy haul train serving the Datong-Qinhuangdao line (hereinafter as DaQin line), of which the brack force is described from the finite element/multi-body train brake system mathematical model that is proposed in this paper. Study the necessity and the problems needing to pay attention to when applying the Locotrol techniques on the heavy haul train. Practical measure the load-timehistory of the coupler force on20,000tonnage heavy haul train running the whole way along DaQin line and select one representative brake process to compare the experimental results with simulated results of which the results show the disciplinary consistency between both methods. Hence the correctness and reasonableness of the longitudinal dynamical model proposed in this paper for the railway train is validated.