Research Of Coal Water Hydraulics Three Function Valve Based On Micro-texture Valve Core And Special-shaped Valve Chamber

Traditional individual hydraulic props and three function valves use emulsion as working medium,which will lead to serious groundwater pollution.And it easy to affect the miners' work environment and health with it spoil.Besides,configuration emulsion need consumption a lot of chemical agent and labor resources,which is cost high.With the increase of people's awareness of environmental protection and production safety,many countries have formulated the relevant laws and the regulations to encourage coal mine support equipment to develop in the direction of safety and environmental protection.Compared with the oil hydraulic,the water hydraulic has many advantages such as safety and environment protection,resource saving and being easy to use,so the popularize and apply of water hydraulic technology in coal mine will be one of the most important development direction of coal mine support equipment in future.Water hydraulic three function valve is core components of individual hydraulic prop using water as working medium.Its key problems of lubrication,wear and cavitation are common problems of other coal mine hydraulic components use water as working medium.The three function valve is taken as research carrier and a new structure of water hydraulic three function valve,with textured valve core and special-shaped valve chamber,have been designed.The water hydraulic three function valve alternatives water replace emulsion as working medium.The method of improving the key problems of lubrication,wear and cavitation of water hydraulic three function valve has been researched.The research results will lay the theoretical and experimental foundation for the practical of water.The main work and conclusions are as follows:1.In order to improve the lubrication and wear characteristics of three function valve core,a new structure of textured valve core has been proposed.Hydrodynamic lubrication model of guiding and sealing section of textured core under complicated conditions have been established.Hydrodynamic lubrication and antifriction mechanism of the textured core under the condition of textured region constant and sealing area variable have been studied.The results show that:(1)The appropriate core texture can produce good hydrodynamic lubrication effect.The pressure of textured valve core surface is greater than the valve pocket surface.And the pressure distribution between the walls is uneven,(2)The diameter width ratio B of the texture should take smaller value.The depth thickness ratio D should take smaller value when Reynolds number Re*is small or B>0.2.It should take bigger value when Re*is high or B=0.2 and its best value near to 1.4.Besides,the higher Reynolds number,the stronger effect of inertia load and cavitation load.(3)Besides the triangle,all the texture morphologies have good hydrodynamic lubrication performance and the sphere morphology has the minimum shear friction and leakage.Further study shows:the straight shaped wedge transition can increase the pressure of the core zone and angle shaped wedge will lead to the core zone contraction,right angle transition can help increase the most-positive pressure and maximum negative pressure of the core zone.Besides,increase the positive-negative pressure zone area ratio can help to increase the dynamic pressure bearing capacity under the same area rate.(4)Hydrodynamic lubrication mechanism research of variable size texture shows that,with the decreases of the valve core overlap length,the total bearing force is increase and shear friction is basically remain unchanged,so as to comprehensive friction on the core surface decreasing when overlap length is greater than 2.5mm.2.Friction and wear test of friction pair have been finished under condition of medium environment and dry friction.The theoretical analysis has been proved to be correct by the experiment.The results showed that:The coefficient friction presents a trend of increase with the load reduce.The texture can help friction pair entering fluid lubrication state when it under low speed,so the texture expand the scope of fluid lubrication.The further research shows that only the reasonable structure of texture have the effect of anti-attrition.With the increase of texture diameter and area rate the friction coefficient decrease first then increase.With the increase of the depth the friction coefficient have the trend of increase gradually.The best texture diameter,depth and area rate are respectively 300?m,40?m and 10%.Besides,the friction coefficient and wear mass are positively related.Smooth testing ring occur severe adhesive and abrasive wear under the condition of dry friction.But textured ring only appear abrasive wear and wear states improved markedly.From the analysis of grinding crack,relative to the smooth specimen the textured specimen's grinding crack size is small,depth is shallow and its distribution has obvious regional.And there are little grinding crack between the two micro-pits in the peripheral direction.The state of grinding crack further illustrate that texture has the important function of the antifriction.3.A new method of improve cavitation by special-shaped valve chamber has been proposed.The CFD models of flow field have been established.The parameters of valve chamber have been optimized and the way of cavitation transfer and weaken have been studied.The results show that:Anti-cavitation ability of two-step throttle structure is strong.The cavitation mainly appeared in the valve port and vortex center of downstream valve cavity of orifice 2.The vortex backflow can help to fill the negative pressure space caused by wall separation of fluid and valve pocket,extrusion the incoming flow at the valve port,restrain incoming flow attached to the valve chamber wall,thus inhibiting cavitation occurs on valve core surface.Besides the introduction of high pressure drainage holes and grooves structure can further reduce the cavitation of valve port.And anti-cavitation ability of grooves is better than that of holes.Finally,in view of three conditions of valve port angle ?1 respectively takes 15°,30° and 45°,the best valve cavity structure and parameters of three groups have been optimized.4.The new structure of water hydraulics three function valve based on special-shaped valve chamber has been put forward.The dynamic characteristics of the model have been studied under the condition of the roof impact.The single factor and multi-factor comprehensive analysis about the parameters influence on the system dynamic performance have been carried out.The response relationship between the components size of three function valve and performance parameters of the supporting system have been determined.Besides,the best combination of factors and levels has been determined.The results show that:Cavity volume dead volume(E factor)almost have no effect on the stress and displacement characteristics of the prop.Reducing the damping hole diameter(A factor),composite length of valve port(B factor),valve core equivalent damping(D factor)and increasing the damping cavity dead volume(C factor)can improve stress and displacement characteristics of the prop.The factors and levels of generate big sinking displacement and small peak pressure basically the same.Ordered factor significantly from strong to weak followed by C,A,D and B factor in turn.The system dynamic performance is good generally when levels of A and D factor are low,B factor is medium level and C factor are high levels.Finally get the best combination is A1B1C3D1(E).5.According to processing the texture on the valve core surface,the machining platform of composite processing with micro-drill and electrolytic has been built.And its processing technic has been researched.The results showed that:Through adopting passivation electrolyte,increasing the cathode rotation speed and reducing feed speed can effectively improve the machining accuracy.Improving the electrolyte concentration and electrolytic voltage can improve the efficiency of electrolysis,but these unfavorable to reduce stray corrosion.The bubble form and current stability occurring in the process of machining are related to electrolysis efficiency and precision.The more electrolytic current stable,the more number and smaller volume of bubbles in bubble layer,the more uniformly distributed of the bubbles,the quality is much better and the machining is more efficient.Finally,get the optimized technological parameters are as follows:selecting NaNO3 as the electrolyte,mechanical processing speed nj=40000r/min,feed speed Vj=10?m/s,electrolyte concentration Ca=4%,electrolytic voltage Ud=5V,electrolytic feed speed Vf =5?m/s,cathode rotation speed n_d=6000 r/min.