Lubrication Characteristics Analysis Of Axial Piston Pump Plunger Pair In Deep Sea Environment

The swash plate axial piston pump has the characteristics of high working pressure and large power density,and is a type of deep-sea hydraulic power source that is currently widely used.The good friction and cooperation between the piston and the cylmder bore and the reliable reciprocation are the keys to output high pressure oil.The piston/cylinder pair is the corresponding main friction pair,and its excellent lubrication performance is the basis for the normal operation of the piston pump.In this paper,the deep-sea environm ent oil source piston pair is taken as the research ob j ect.Starting from the change of the environmental parameters to the properties of the oil medium,the oil film lubrication characteristics of piston/cylinder pair in underwater environment are studied.The main contents are as follows:(1)This paper analyzes the working principle of the underwater pressure compensated piston pump,and points out that the deep sea environment affects the oil film lubrication by changing the physical properties of hydraulic oil.Based on the analysis of the environmental pressure and sea water temperature under the vertical sea depth,the variable water depth environmental model is established.Considering the change of the actual water depth,combining the water depth model and the medium properties,the dynamic change model of oil in varying water depth condition is established with pressure and temperature as the parameters,and the change rule of oil viscosity,density,bulk modulus and other medium parameters under variable water depth condition is obtained.(2)Modeling and solution of hydrodynamic lubrication model of piston pair in deep water environment.This paper describes th e tilt attitude of the piston in the cylinder bore,derives the oil film thickness equation,and combines the medium variable viscosity model,variable density model,and Reynolds pressure model to establish hydrodynamic lubrication model,solves the pre ssure control equation by using the finite difference method to obtain the oil film pressure distribution,bearing capacity and oil leakage.Based on the steady-state lubrication model,given the eccentric position of the piston,the effect of the piston's own motion parameters on the lubrication performance of the friction pair is obtained.(3)Research on dynamic lubrication characteristics in whole cycle of piston pair in deep sea environment.Considering the time-varying load and position of the piston in a cycle,the force on the piston is analyzed,and the dynamic balance equations are established.With the help of MATLAB programming tools,the coupling relationship between the external force/torque of the piston and the supporting force/torque of the oil film is solved by using the one-dimensional golden section method and th e multi-dimensional coordinate rotation method,the change rules of oil film thickness distribution,pressure distribution,axial friction and oil leakage of the plunger pair in a complete cycle are revealed.Then a variety of simulation conditions is set up to investigate the changes in the main performance in dicators of the piston pair under varying load pressure,spindle speed,and swash plate inclination respectively.(4)The effect of piston surface texture on the lubrication performance was studied.In order to avoid the uneven oil film pressure distribution of the piston pair in the deep sea environment,which leads to the instability of oil film lubrication,a single annular groove structure parameter was selected for simulation analysis.The comparison found that the surface texture can improve the oil film lubrication performance of the piston pair.