Research On High Pressure,super Large Flow And High Water-based Unloading Valve

Coal is the main basic energy source in our country and an important pillar industry that promotes the development of the national economy.With the development and integration of intelligent manufacturing technology,industrial automation technology,and wireless communication technology,automatic,intelligent and unmanned coal mining technology has been initially applied to modern coal mining and become the future development trend.Due to the increasing demand of domestic fully mechanized working face equipment with large mining height,emulsion pump station with high pressure and large flow has become one of the research focuses of modern mining equipment.As the main component of pressure control in emulsion pump station,unloading valve will inevitably face the problems of poor dynamic performance,large hydraulic impact and serious cavitation damage under the complex working conditions such as high pressure,large flow rate and frequent opening and closing.Based on the working conditions of unloading pressure 40MPa and nominal flow rate 1800L/min,this paper makes a series of in-depth research on the structural parameter design,theoretical modeling analysis and simulation optimization of the unloading valve.As a result,the key problems such as dynamic characteristics,hydraulic impact and cavitation damage have been optimized.By studying the development status of unloading valve at home and abroad under similar conditions,the parameter performance indexes and main problems of unloading valve are clarified.The internal working mechanism of the unloading valve is analyzed,and the structure and size of the unloading valve are designed.By establishing the equivalent physical model of the unloading valve,the static and dynamic characteristics of the unloading valve are analyzed and deduced theoretically.Aiming at the pressure and flow rate characteristics during the opening and closing process of the unloading valve,the unloading system under the two control modes of mechanical and electromagnetic is simulated.The effects of the diameter and length of the orifice,the diameter of the ejector rod and the response time of the solenoid pilot valve on the dynamic performance of the unloading valve are analyzed.It is found that the length and diameter of the orifice will affect the pressure fluctuation range and flow overshoot of the unloading valve,and further affect the stability of the unloading valve.The diameter of ejector rod will affect the recovery pressure and unloading frequency of unloading valve.The response time of the solenoid valve will affect the response characteristics and unloading cycle of the unloading valve,thereby affecting the opening and closing characteristics of the unloading valve.The collision dynamics simulation of the check valve assembly which is most affected by hydraulic impact and weakest in structural strength is carried out.By analyzing the stress and deformation of the check valve when it is closed,it is verified that the structural strength of the check valve meets the performance requirements of the unloading valve.Aiming at the problem of cavitation damage of the unloading valve,the flow field simulation analysis of the unloading valve is carried out.By setting the cavitation model,the fluid movement in the main valve cavity under different valve openings is studied.And the velocity,pressure and gas phase distribution of the flow field in the main valve cavity are obtained.The results show that when the fluid medium flows through the valve port,cavitation will occur due to the sudden increase in flow velocity and the sudden drop in pressure.When the bubbles generated by cavitation collapse,the damage to the inner surface of the part is the phenomenon of cavitation erosion.With the increase of opening of main valve,the flow rate passing through the valve port increases,the pressure difference between the front and rear of the valve port decreases gradually,and the cavitation erosion phenomenon is correspondingly weakened.Therefore,when the valve port is at a small opening,the flow field in the valve cavity should be more worthy of attention.Through the research on the mechanism of cavitation,the structure of the unloading valve is optimized,and a special-shaped valve port is innovatively proposed.When the fluid medium flows through the valve port,it can produce the effect of diversion and hedge,which makes the pressure of valve port change from sudden change to gradual change,and avoids the sudden increase of flow velocity.By comparing the speed,pressure,and gas distribution of the flow field before and after optimization,it can be found that the gas volume fraction in the main valve cavity is reduced after optimization,and the gas distribution area is also significantly reduced.The results show that the structure satisfies the flow capacity requirements of the unloading valve,and improves the anti-cavitation ability of the unloading valve.In this paper,through product research,theoretical derivation,model simulation,optimization design and other processes,the dynamic characteristics,hydraulic impact and cavitation damage of the unloading valve are comprehensively analyzed and studied,which lays a theoretical foundation for the design of a safe,reliable and durable unloading valve.