Simulation of a railway pneumatic brake system

In long trains equipped with pneumatic brake systems, the decay in pressure along the pipeline can be significant, altering the instantaneous braking force distribution from the first to the last car. Knowing the force distribution and the time until the brake forces stabilizes is important to design adequate vehicles and tracks. In this paper, a mathematical model that reproduces the dynamic response of the railway pneumatic brake system on all its operations is presented. In order to model it, the behavior of the fluid (compressed air) and the brake valves set were studied, so that it became possible to model the mechanical interactions in the system due to pressure variation in the pipeline. Based on mass conservation, a non-linear mathematical model was developed to describe the brake pipe, the control valves, the reservoirs and the brake cylinders. Results for actuation time in the brake operation in a 50-wagon convoy with double-wagon (only one valve to each pair of wagons) using AB valve are presented and compared to real data. A 100-wagon convoy was also simulated and its actuation time was compared to the 50-wagon one.