Numerical Simulation Of Cavitation Flow In Poppet Valve Port Based On OpenFOAM

In the numerical simulation of the flow in the hydraulic poppet valve port based on Open FOAM,considering the compressibility of the two phases in the phase change process of oil and oil vapor,the multiphase flow mixing model was selected and the positive pressure equation with compressibility was added to describe it.The k Omega SST model is chosen as the turbulence model,which is more accurate in predicting the reverse pressure gradient and facilitates the capture of attached cavitation phenomena.In terms of wall function,kq RWall Function is used to correct turbulent kinetic energy,nutk Wall Function is used to correct viscosity,and omega Wall Function is used to correct turbulent energy dissipation rate.The equation solving method adopts the PIMPLE algorithm,and the variables in each time step during the solving process are discretized using different methods according to the situation to achieve stable solution.The numerical simulation results indicate that this method can capture the generation,development,and collapse process of bubbles in the valve seat,valve core,and downstream of the valve cavity.The cavitation mechanism was analyzed from a microscopic perspective and numerical simulation of cavitation flow at the cone valve port was conducted based on Open FOAM.By analyzing the cavitation mechanism at the valve port through gas phase cloud maps,velocity cloud maps,and pressure cloud maps,it is concluded that cavitation initially occurs at the sudden increase in flow area,i.e.at the upper edge of the chamfer.The high-speed flow passes through this area,and the fluid in the low-speed area undergoes energy transfer and forms eddies.At the solid-liquid interface where the geometric shape of the cone valve undergoes a sudden change,gaps first appear,creating bubbles.Subsequently,the bubbles move downstream and gather to form a cavity,until the cavity reaches the threshold and is sheared into a small cavity by the eddy current reflux,resulting in collapse.Instantaneous pressure pulses will be generated during collapse.The structural parameters of the cone valve,such as the angle of the cone valve core,the length of the valve seat chamfer,and the opening of the valve port,affect the cavitation flow characteristics of the cone valve port.The larger the angle of the cone valve core,the closer the cavitation position is to the opening,the more intense the cavitation,and the more unstable the flow;The longer the chamfer length,the smaller the cavitation volume at the valve port;The larger the valve opening,the more severe the cavitation.The flow field parameters of the cone valve,such as inlet flow velocity and velocity fluctuations,have a significant impact on the cavitation flow at the cone valve port.The larger the inlet flow rate,the more severe the cavitation phenomenon and the longer the cycle;The frequency of sinusoidal flow velocity fluctuations affects the cycle period of cavitation phenomenon,and the higher the frequency,the more obvious the flow instability and cavitation effect.The amplitude within ±5% of the stable flow rate has little effect on the degree of cavitation,and it begins to have a significant impact when it exceeds 10%.