Int. J. of Vehicle Design, vol. 10, no. 4, 1989. Printed in UK Dynamic response of a railway vehicle air brake system M.A. Murtaza* and S.B.L. Gar& *Joint Director, Research Designs and Standards Organisation, Lucknow, India tprofessor and Head Mechanical Engg. Dept. M.N.R.Engg College, Allahabad, India Abstract: A Railway Vehicle Air Brake System has been analysed by considering its system kinematics and fluid mechanics. The kinematic model is represented by a single degree of freedom equation of motion, yielding a formed solution. Air flow is assumed as incompres- sible and unsteady. Corrections for instantaneous mean density have been made and the Runge- kutta method of numerical integration has been used for solving the governing differential equation. Analytical results are in good agreement with the laboratory data. Reference to this article should be made as follows: Murtaza, M.A. and Garg, S.B.L. (1989) 'Dynamic response of a railway vehicle air brake system', Int. J. of Vehicle Design, vol. 10, no. 4, pp. 481-496. Keywords: Brakes, brake performance assessment, fluid mechanics, kinematics, railway air brake system. 1 Introduction A Railway Air Brake System is basically comprised of two systems. A train system and a vehicle system. The train system comprises a driver's brake valve in the locomotive and a brake pipe along the train's length which communicates braking demand along the length of the train as per the braking requirement, based on the locomotive driver's train handling needs. Whereas the vehicle system is comprised of an auxiliary reservoir, brake cylinder, a control valve and allied pipes and cocks provided on each vehicle. The control valve senses the braking demand through the brake pipe and accordingly the brake cylinder is connected to the auxiliary reservoir, so that the brake cylinder is charged to the desired pressure in order to actuate brakes. In the case of a twin pipe air brake system an additional feed pipe runs along the length of the train so as to charge the auxiliary reservoir continuously. In a graduated release air brake system not only the application of the brakes but also their release can be carried out in accordance with the driver's requirements, whereas in a direct release air brake system the driver has no such discretion on release. In the past attempts have been made to simulate brake application by using laboratory data and then approximating the brake cylinder pressure development curve by two or three straight lines [5, 61. Whereas Hart and Grejda [8] and AAR report [7] have used empirical equations developed on the basis of laboratory data to simulate brake cylinder pressure. These approaches are aimed at assessing braking performance of a vehicle or a train in order to compute braking distance or to use them in a train simulation model for the braking component. These methods are an approximation and are limited to the set-up used for generating laboratory data. In contrast to past studies in the present approach design details have been considered of a vehicle brake system and with this technique it is possible to assess design perform- ance as well. Copyright @ 1989 Inderscience Enterprises Ltd., UK.