Study On Flow Characteristics Of Valve Orifice And Steady-State Flow Force In Hydraulic Cone Valve

Hydraulic cone valve is widely used in hydraulic system because of its strong flow capacity,good sealing,simple structure and low cost.But the hydraulic cone valve will be affected by the axial steady-state flow force in the working process,which will cause the vibration and noise of the valve core and valve body,and then affects the accuracy and stability of the hydraulic system.Therefore,in this paper,theoretical,numerical and experimental methods are used to study the relationship between the opening,flow and pressure difference of the hydraulic cone valve,the variation characteristics of the flow field inside the valve cavity,the variation of the force and the pressure on the cone tip surface of cone valve core,and then the influence of different factors on the steadystate flow force characteristics is discussed.Based on the momentum theorem,the force acting on the control body in the upper and lower valve cavities of the cone valve is analyzed.Combined with Bernoulli equation,the force acting on the control body by the valve seat is calculated,and the mathematical calculation model of the axial steady-state flow force acting on the cone valve core under full opening is derived.The two-dimensional axisymmetric model of the cone valve is established,and the flow field characteristics in the valve are obtained by numerical simulation.At the same time,the steady-state flow force experimental system is designed and built,and the influence factors of steady-state flow force are analyzed.The change of fluid flow direction of hydraulic cone valve will significantly change the flow field of hydraulic components.Whether it is inlet throttle or outlet throttle,the throttle is the area with the most dramatic pressure change,and there is a high beam.Under the same conditions,the change of fluid flow through the hydraulic cone valve is less than 2%,but the steady-state flow force is obviously different.With the increase of the opening,the axial steady-state flow force on the cone valve core increases first and then decreases.When the opening is small,the steady-state flow force of the valve core under different flow directions is similar,but when the opening is large,the steady-state flow force under outlet throttle flow direction is larger.When the hydraulic system works for a long time,the oil temperature will inevitably increase significantly,which not only affects the flow state of the fluid in the hydraulic valve,but also may affect the normal work of the hydraulic system.When the temperature of the oil increases,the viscosity of the oil decreases,the flow of the fluid increases,the pressure in the low pressure area of the lower valve cavity increases,the turbulence intensity at the flow section of the valve port decreases,the viscous friction between the oil and the valve core decreases,the axial force on the valve core decreases,and the steady-state flow force increases.In addition,pressure difference,opening,half cone angle of valve core cone tip and valve core diameter are also factors that affect the valve port characteristics and steady-state flow force.The orthogonal test with four factors and four levels is designed.The main and secondary order of the factors influencing the axial steady-state flow force of the valve core is obtained by the method of extreme difference analysis:pressure difference,opening degree,half cone angle of the valve core cone tip and diameter of the valve core.The effects of pressure difference and opening on the steadystate flow force characteristics of hydraulic cone valve are analyzed by theory,numerical simulation and experiment.The results show that the pressure difference between inlet and outlet increases,the steady-state flow force increases,the opening of valve core increases,the steady-state flow force increases first and then decreases,and the steady-state flow force is the largest at 2mm opening.The thesis has 55 figures,3 tables and 78 references.