Research On Theoil Film Characteristics In The Gap Between Piston And Cylinder In Pump

Piston pump is a complex product of Fluid-Thermal-Structural coupling.It mainly consists of three friction pairs: piston pair,slipper pair and valve pair to ensure energy conversion efficiency and service life.The piston deputy is mainly composed of piston and cylinder block.The two parts cooperate with each other to realize the periodic change of the volume of the chamber,and then realize the functions of oil absorption,pressurization and drainage.Piston pair is one of the most important friction pairs of piston pump.Its performance directly affects the life and working efficiency of piston pump.However,at present,the interaction of kinematics,dynamics and hydrodynamics,materials science and thermodynamics of piston pairs is still not clear,and there is no mature theoretical support.Therefore,this paper carries out research work from both theoretical and experimental levels.The main research contents are as follows:(1)Combining the structure,movement and force of the piston pair,the motion and force model of the piston pair is established and the kinematics simulation is carried out.(2)A fluid-solid coupling oil film model of piston pair is established and solved numerically.The Newton-Raphson method is used to solve the Reynolds equation and the oil film thickness equation for the eccentricity of the piston in parallel,and the oil film pressure discrete equation is obtained.Then the oil film pressure discrete equation is solved by the over-relaxation iteration method to obtain the oil film pressure distribution.Finally,the elastic deformation of piston surface is calculated by finite element method.(3)The oil film thickness,pressure and viscous friction of the piston pair are calculated numerically,and the influence of different load pressures and rotational speeds on the minimum oil film thickness and viscous friction is analyzed.(4)Designed and built a multi-physical field coupling piston pair oil film characteristics test bench and matching test system.The oil film thickness,oil film pressure and viscous friction test of piston pair were carried out under different load pressure and spindle speed conditions,and the test and simulation results were compared and analyzed.Theoretical analysis and experimental results show that:(1)when elastic deformation is taken into account,oil film characteristics change;(2)the greater the load pressure,the higher the spindle speed,the more obvious the effect of elastic deformation on oil film thickness;(3)viscous friction increases with the increase of load pressure and spindle speed;(4)the appearance of elastic deformation causes the increase of oil film shear stress,which leads to the increase of viscous friction.This conclusion proves the relative accuracy of the proposed multi-physical parameters coupled oil film thickness and pressure distribution model,which can effectively predict the lubrication performance of piston pairs and guide the structural optimization of piston pairs.