Flow Characteristics Of Large Flow And Water Based Electro-hydraulic Proportional Valve Port For Mining

As the core element of the hydraulic system of the hydraulic support,the hydraulic valve makes the hydraulic support support by controlling the hydraulic cylinder,so the performance of the hydraulic valve is related to the safety and production efficiency of coal mine.At present,the support hydraulic system all uses the switch type electro-hydraulic directional valve,due to its working mechanism,the flow can not be controlled,and can not achieve fine control of the support action,in addition,the switch valve in the opening and closing will produce a large hydraulic impact,will damage the hydraulic components.Based on the above problems,this paper combines the electro-hydraulic proportional control technology with electro-hydraulic directional valve,and proposes a large flow and high water-based electro-hydraulic proportional valve for mining.Because the working medium is water-based liquid,physical and chemical characteristics close to water,and water vaporization pressure is high,cavitation is easy to occur,make the valve core cavitation and vibration.In addition,the large flow valve core flow force is also large,cavitation and flow force will affect the flow stability of the valve and reduce the control accuracy.Based on the above two factors,the cavitation characteristics of pilot valve and the hydrodynamic characteristics of main valve are studied.In order to realize proportional control,a new proportional valve scheme of main valve action asynchronously following pilot valve action is proposed.The pilot inlet valve is embedded in the main spool,the main valve is opened following the pilot inlet valve.The pilot outlet valve is connected to the main valve control chamber,the main valve is closed following the pilot outlet valve.The pilot inlet valve and outlet valve opening and flow can be controlled by controlling the driving motor,and then the main valve can be opened and closed.By studying the structure of two-stage throttle port,the pilot outlet valve port is designed as two-stage throttle port to restrain cavitation.Two-phase flow simulation analysis is carried out for two-stage throttle port with different parameters.Different half-cone angles of valve cores will affect the distribution of pressure,velocity and vapor volume fraction in the flow field.When the halfcone angle of the valve core and the valve opening increase,the partial pressure of two-stage throttling is weakened and the cavitation phenomenon is strengthened.For different half-cone angle structures of valve core,the critical cavitation index is different.When the outlet back pressure is set to a certain value,the cavitation index will be greater than the critical cavitation index.At this time,the flow field basically has no cavitation,indicating that the back pressure can effectively suppress the cavitation phenomenon.By simulating the flow field of the main valve,the flow characteristics of the main valve under different pressure difference,opening degree and orifice shape are obtained.In order to optimize the valve orifice of the main valve,the flow field of the main valve under different spool cone angle,orifice shape and orifice angle is simulated,and the flow force curve is obtained.The force difference on the conical surface of the main valve under different main valve half-cone angle is large,which affects the fllow force value;When the orifice is triangular,the flow force is the largest,and the flow force of the rectangular orifice and the circular orifice is smaller and the numerical value is approximately the same;When the orifice angle is 60°,the flow force is the maximum,and when the orifice angle is 120°,the fow force is the minimum,the main gap is on the orifice and axial flow path;The outlet back pressure can increase the flow pressure and restrain the cavitation effectively,but it has little effect on the hydrodynamic force.This paper belongs to the preliminary structural design of large flow and high water-based electro-hydraulic proportional valve for mining.The research conclusion can provide a theoretical reference for the development of large flow and high water-based electro-hydraulic proportional valve for mining.