Study Of A New Double Ratio Relay Valve

The relay valve is a very key component in the braking system of EMU,which plays an important role in the safety and reliability of the brake system.According to the ratio between the output pressure and the pre-controll pressure,relay valve can be divided into single ratio relay valve,double ratio relay valve,multi ratio relay valve and adjustable ratio relay valve.The double ratio relay valve is also known as two stage pressure control relay valve,which outputs two control pressures under different speeds.That is to say,high brake pressure is output under low speed conditions while low brake pressure is output under high speed conditions,in order to adapt to the different adhesion condition of high-speed train under different speed conditions.At present,the majority of the study at home and abroad is about the analysis of dynamic performance of the relay valve by using the AMESim software.However,there is no information in the literature specifically regarding the study of internal gas flow characteristics,aerodynamic force of spool,flow coefficient and so on.The study is based on the fluid simulation software Fluent and multidisciplinary simulation software AMESim.Fluent is used to analyze the flow field characteristics of double ratio relay valve.Through transient and steady flow field simulation,data of aerodynamic force of spool and flow coefficient are obtained.The data obtained by Fluent are loaded into the AMESim simulation model,and the static and dynamic simulation of the double ratio relay valve is carried out,and the optimal design is carried out.The main contents of this paper are as follows:1.The working principle of the double ratio relay valve is analyzed.According to the braking characteristics of the high-speed EMU braking system,aiming at the design target of the ratio between the output pressure and the pre-controll pressure,the structure design of the double ratio relay valve is carried out,so that its input and output characteristics meet the requirements.Through the force analysis of the valve spool and the gas flow analysis,the mathematical model of the double ratio relay valve is set up.2.Fluent is used to simulate the steady state of the duouble ratio relay valve,and the parameters such as the aerodynamic force of spool and the flow coefficient under various opening conditions are obtained.By using the dynamic mesh technology and writing the valve movement equations to the UDF,the transient flow field of double ratio relay valve in the braking condition were simulated,obtained characteristics of spool movement,and the flow field characteristics of the chamber as well as the dynamic performance of the double ratio relay valve.By comparing the steady state simulation and transient simulation,it is found that the aerodynamic force of the spool is found to be consistent.The steady state aerodynamic force obtained by steady state simulation can be used to replace the spool aerodynamic force.3.The simulation model of double ratio relay valve is established by using AMESim.The aerodynamic force of the spool calculated by Fluent and the flow coefficient calculated by Fluent are loaded to the simulation model through the calculation modul by fitting,so as to correct the simulation model.Based on the modified simulation model,the effects of various parameters of the double ratio relay valve on its performance are studied,including the following parameters: the stiffness and preload of the piston spring,the stiffness and preload of the spool spring,the orifice diameter and the diameter of the piston a and the piston b.Under the AMESim platform,NLPQL algorithm is used to optimize the double ratio relay valve.