Research On A High-pressure Pneumatic Solenoid Valve With Parallel Spools

An underwater driving system including air tank,control valve,cylinder,load,etc,is driven by high-pressure compressed air.In order to realize the high speed launching of the load driven by the cylinder,a high-pressure solenoid valve with high speed,high and adjustable flow rate is required as the control valve in the driving system.Current high-pressure pneumatic solenoid valves are typically pilot operated types.Under this structure,there is a mutually restricting relationship between high flow rate and fast response.Namely,the larger the size of the valve is,the slower the response velocity of the valve will be.And they do not have flow regulation function.According to current reports and market research,no commercially available high-pressure solenoid valves can meet the demands of both high flow rate and fast response of the driving system.In order to resolve this problem,a novel valve design with parallel spools is proposed here.A series of research work on the valve is carried out,including structure design,mathematical modeling,simulation,optimization and performance tests,etc.Firstly,based on the analysis of the mutually restricting relationship between high flow rate and fast response for traditional pilot operated solenoid valve,it is found that structure innovation is the key to solve the problem.A high-pressure pneumatic solenoid valve with parallel spools design is proposed.The design idea is that three smaller sized valves with a fast response are grouped together in a parallel configuration to improve flow capacity.Under the structure the valve will have both the characteristics of high flow rate and fast response.In addition,the flow rate of the valve is adjustable.The overall structure of a high-pressure pneumatic solenoid valve with 3 parallel spools is designed.In order to validate the overall performance of the valve with parallel spools,numerical simulations of the parallel-spool valve are carried out to study the flow field and the flow capacity by using CFD software.Due to the deep analysis of the working process of the high-pressure pneumatic solenoid valve,the mathematical model of opening process is established.According to the dynamic characteristics of the opening process,the opening response time can be subdivided into armature preparation time,armature movement time,exhaust time of the control chamber and movement time of the main valve spool.The corresponding formulas to solve the response times are derived based on reasonable simplifications and assumptions,which provide a theoretical basis for the study of the effect of main structure parameters on its opening response time.According to the mathematical model established,the simulation research on the opening response was carried out.The effect of main factors including exciting voltage,working pressure,diameter of the pilot valve,diameter and stroke of the main valve spool,etc,on the response time of opening process was analyzed.In order to reduce the opening response time of the valve,a parameter optimization program was designed by using Multi-population Genetic Algorithm.After optimization the opening response time of the valve is able to meet the demand of the underwater driving system.Based on the previous work,the experimental prototype of the high-pressure pneumatic solenoid valve was developed and the corresponding test systems for the opening response time,the effective sectional area,the leakage and the performance of the valve in the driving system were designed and established.In order to obtain the opening response time,a main valve spool displacement transfer device was designed.In the device,a rubber tube was used as the flexible sliding seal between the push rod and the main valve body.Under the condition of reliable sealing and no affect on the main valve action,the accurate opening response time which is a key performance parameter can be obtained through direct measurement of the opening process of the main valve by using the test device.At the working pressure of 10MPa,the opening response time of the valve tested is 48.2ms.And the synchronicity between the parallel spools is good.Under the condition of three main valves opening simultaneously,the effective area of the valve is 119.8mm2 by using the method of discharging at the velocity of sound.And the three flow rates of the valve are 890L/s,1600L/s and 2100L/s.According to the mathematical model of the solenoid valve established,the mathematical model of the driving system was built.Then the simulation on the effect of the number of open main valves and the pressure of the air tank on the velocity of the load was carried out.A principle of equivalent mass load was put forward and used in the simulator design of the driving system.The simulator of the underwater driving system was established to test the performance of the valve developed in practice.The test results show that in case of the security conditions permit,the experimental results and the simulation results of the load speed of the simulator have good agreement which confirms the validity of the established model of the driving system.According to the fitting curve of the experimental data,at the working pressure of lOMPa,the load can reach the speed of 15.2m/s at the end of travel,which is able to meet the demand of the driving system.The working pressure,the opening response,the flow capacity and three-step flow rates of the valve developed are able to meet the demands of the driving system.The success of the valve with parallel spools provides a new design idea for the structure design of the high-pressure solenoid valve,and show good application prospect.