Numerical Simulation Of Transient Periodicity And Effect Of Cavitation In Poppet Valve

Hydraulic poppet valve has the characteristics of simple structure,good sealing performance and strong anti-pollution ability,which makes it one of the most common valve structures in hydraulic valves.Cavitation of valve por t and its associated phenomena such as vibration and noise often occur in the working process of poppet valve,which has become one of the important sources of vibration,noise,heat and stability problems of hydraulic system.Cavitation at the valve port of poppet valve is a high-speed transient flow phenomenon,which needs further study due to its complexity.At present,experimental research can only explain part of its mechanism,while numerical simulation can overcome experimental limitations.In this paper,the multi-phase flow numerical simulation technology and theoretical analysis are used to make an in-depth study and summary of the transient cavitation flow of the poppet valve under the throttle and overflow conditions.The main research work of this article are:The turbulent viscosity modified RNG model and the turbulent kinetic energy modified Zwart cavitation model were used to analyze the transient cavitation flow of the throttle valve throttle condition.The results show that the periodic cavitation flow at the valve port of poppet valve consists of three stages: cavitation inception,development and collapse.The periodic frequency of cavitation is 1182 Hz,of which the development stage accounts for about 81% of the whole cycle,and the pres sure fluctuation when the cavitation collapses completely can reach 4 MPa.The cavitation development stage promotes the increase of valve port velocity,and the cavitation collapse reduces the valve port velocity,so the fluctuation of periodic cavitation mass flow rate can reach 41% of the average value Velocity vortex and its turbulent kinetic energy are important conditions for cavitation migration,and turbulent kinetic energy at the junction of forward and reverse jet regions promotes the development of large-scale cavitation;The valve cor e surface force changes from 33 N to 116 N when the cavitation collapses completely.The influence of the turbulence equation viscosity correction function power index constant term n and oil viscosity will not only affect the cavitation morphology of valve port,but also have a significant impact on the cavitation cycle frequency.When n?2,the cavitation of cone valve port is unsteady and non-periodic.When 4?n?30,the periodic frequency will increase from 400 Hz to 1200 Hz.When 2?n?30,the gas volume fraction and mass flow rate in the calculation domain decrease by 36.4% and 4.1%,and the fluctuation peak value of valve core surface force changes from 34.6N to 124 N.When n is 10,the oil temperature increases from 10 ? to 70?,the cavitation cycle frequency increases from 400 Hz to 1100 Hz,and the fluctuation peak value of valve core surface force changes from 29 N to 110N;Not all periodic cavitation will cause large-scale pressure pulsation,but only when the cavitation collapses completely will it cause large-scale pressure fluctuation in the flow field.When the poppet valve is in overflow condition,the cavitation flow in the flow field will become extremely complex,and the cavitation incipient position is no longer limited to the valve core or valve body surface,and cavitation incipient position will also occur in the vortex.The cavitation flow not onl y includes incipient,development and collapse,but also is accompanied by the merger and division of cavitation.According to the cavitation initial position,the influence of valve seat structure on valve port cavitation is discussed.The results show that by changing valve seat structure,the cavitation gas content can be reduced by 20%,the mass flow rate can be increased by 34.7%,and the periodic frequency can be reduced from 1182 Hz to 1104 Hz.