Investigation into the braking performance of high-speed trains in the complex braking environment of the Sichuan-Tibet Railway

The Sichuan-Tibet Railway is an east-west rapid plateau railway under construction from Chengdu to Lhasa. One of its most remarkable features is the high altitude and notable altitude fluctuations. High altitudes will result in low atmospheric pressures and temperatures. The freezing caused by low temperatures will lead to low wheel-rail adhesions. Altitude fluctuations will generate complex spatial railway tracks. To investigate the braking performance of a train in such a complex braking environment, a train spatial dynamics model, a model of a direct pneumatic brake system and a model of a braking control strategy are constructed. A comprehensive analysis model for investigating the braking performance of high-speed trains in a complex braking environment is proposed based on the constructed train spatial dynamics model, direct pneumatic brake system model and braking control strategy model. A simulation computation platform for train braking performance analysis on the Sichuan-Tibet Railway is established based on SIMPACK, AMESim, Simulink and their interfaces. The braking performance under the different altitudes, different spatial railway tracks and low adhesions are analysed in detail and summarized. Computation time are compared in different altitudes and track conditions. Computational efficiencies of the dynamic model with multi-thread parallel computation are discussed. The results indicate that an increasing altitude and the alteration of railway track conditions have a remarkable influence on the braking distance, brake cylinder pressure, instantaneous deceleration, maximum wheel-load reduction rates and maximum longitudinal impact forces of high-speed trains. The track conditions in the dynamic model have a greater impact on the computation speed. Compared to single-thread parallel computation, the computational efficiency using 2-thread parallel computation can be promoted by 22.97%. These results will provide a reference for the Sichuan-Tibet Railway design and the optimization of train braking systems.