The Research On Motion Of The Poppet In The Fluid-structure Coupling Calculation And Experiment

Single stage pressure regulating cone valve is widely used in industry as a hydraulic base.The single-stage pressure regulating cone valve is mainly composed of valve core,seat and spring,which can be used for direct work in the hydraulic system of the main valve,but also as a pilot valve to adjust the working pressure of the system,as a pilot valve,its pressure regulating precision,the stability of the movement of the valve,etc gets more attention.For pilot stage pressure regulating cone valve,due to its own small damping coefficient,it is more vulnerable to the disturbance of the change of inlet flow,resulting in vibration cavitation and other unstable phenomena,serious will trigger safety accidents.Therefore,it is of great significance to study the single-stage pressure regulating cone valve to improve the reliability and stability of the whole hydraulic system.This paper adopts the method of visualization test,Comsol fluid-solid coupling simulation and theoretical analysis.The instability of flow field at the valve orifice of single pressure regulating cone valve,the stress on the valve core surface,the oil flow at the valve orifice and the natural frequency of the valve core immersed in the oil are studied.The specific research contents are as follows:Combined with the literature,the jet flow at the valve port is analyzed by using the jet flow theory,and it is pointed out that the wall jet flow is the key factor affecting the flow shape of the valve port.By means of visual test,the trajectory of jet flow and the image of flow instability of valve port are obtained.In the valve orifice flow field of flat-end poppet and ball-end poppet,the wall attachment effect of the submerged jet can be observed at the valve orifice,and when the wall attachment jet exists,a stable annular vortex can be formed at the convex head,and a low-pressure backflow zone can be formed at the valve line,and the flow field at the end of the valve orifice has good stability.When the flow field at the end of the valve port of the ball-end poppet valve core is unstable,the main factor causing the instability is that the submerged jet at the valve port cannot form a stable wall jet.The series damping hole in front of the single-stage pressure regulating cone valve can effectively inhibit the occurrence of cavitation,but from the perspective of flow field visualization,the series damping hole cannot effectively improve the flow field stability of the valve port.It is not clear why ball head spool cannot form an effective wall jet at the valve orifice in some cases.Through the method of fluid-solid coupling simulation,the force on the spool surface of the spool and the spool of the spool of the cone valve with flat head and the spool of the cone valve with ball head and the streamline direction of the valve port are studied.By setting the condition of whether there is damping hole or not,the influence of the submerged jet in the damping hole and the influence of the difference of spool surface structure are studied.It ispointed out that the reason for the good flow field stability of the flat cone valve with damped hole structure is that two stable annular vortexes can be formed at the front end of the valve port of the flat cone valve with damped hole structure.According to the simulation results of flat head valve and ball head valve,combined with the advantages of both,the structure of the valve is improved,and the improved results are analyzed and studied by simulation.Combined with the spool mechanical balance equation,flow equation and continuity equation,the transfer function method is used to analyze the dynamic characteristics of the single-stage pressure regulating cone valve without damping hole,and the natural frequency of the valve immersed in oil is calculated.The experimental method is used to obtain the vibration frequency of the valve in the actual working process,and compared with the calculated natural frequency of the valve,it is concluded that the calculated natural frequency of the valve immersed in oil by the traditional transfer function method is too small.Then the natural frequency of the spool is calculated by means of fluid-solid coupling simulation.The problem of distortion of steady state hydrodynamic calculation in natural frequency calculation by traditional transfer function method is explained.It provides a basis and reference for the future selection of single-stage pressure regulating cone valve,thus avoiding the occurrence of coupling resonance.The influence of the difference of spool surface structure on the force of spool and the flow of oil at valve orifice is studied in this paper,which is of positive significance for optimizing spool structure to improve the stability of flow field at valve orifice and thus to improve the service life of spool.In this paper,the research on the natural frequency of the valve core immersed in oil provides reference and basis for the selection and trial-manufacture of the single-stage pressure regulating valve,which is conducive to avoiding its coupling resonance in the system.