27. Flow Path Optimization of Pneumatic Valves Through CFD Analysis

Relay emergency valves are typical pneumatic flow control valves which are primarily used in air brake vehicles to speed up the application and release of rear axle(s) brakes. This valve will also have additional provision to apply the trailer brake automatically in the event of accidental decoupling of trailer. The relay emergency valve will graduate, hold, and release of air pressure from the brake chambers to which it is connected. The relay emergency valve is used to reduce the response time of brake applications on heavy-duty vehicles. In order to achieve higher valve response, the valve should yield high flow rate for a wide range of operating pressures. Higher flow output can be achieved with the minimum flow restriction in the valves. To achieve different product functions, the assembly will have subparts like piston, springs, seals, etc. which will restrict the flow passage. To achieve high flow rate without sacrificing the product function, the valve flow area should be maximum. Hence, computational fluid dynamics (CFD) can be utilized as a useful design tool to optimize the flow area of relay emergency valves and also to study the effect of flow restrictions. This paper covers the optimization of the flow path by finding the nominal flow diameters as per ISO 6358. A thorough CFD analysis with several design iterations of the valve has been made to improve and finalize the nominal flow diameter with the required flow rate at the outlet to meet the design requirements. The theoretical results are in good agreement with the experiments.