Research On Lubrication And Drag Reduction Mechanism And Friction And Wear Of Slipper Pair With Bionic Non-smooth Surface In Seawater Axial Piston Pump

The rational development and utilization of the rich natural resources in the ocean to solve the population,resources and environmental problems facing the world have promoted the rapid development of the seawater hydraulic transmission technology.Compared with the traditional oil hydraulic system,the seawater hydraulic transmission system has so many advantages,such as easy access to its working medium,clean,safe and good compatibility with marine environment,etc.that it has gained increasing attention and applications.The seawater axial piston pump is the core power element of the seawater hydraulic systems.The slipper pair of pump will be very vulnerable to corrosion and abrasion when running in the marine environment of low viscosity,poor lubrication,high electric conductivity and vaporization pressure,which seriously restricts the development of seawater hydraulic components and systems.Therefore,in the research of this paper,the bionic non-smooth surface effect is introduced into the slipper pair of seawater axial piston pump based on selecting the optimal matching materials.Through theoretical analysis,numerical simulation and experimental study,this paper will explore the mechanism of lubrication,drag reduction and wear resistance to improve its load-carrying capacity,friction and wear performance as well as its service life.Thus,this research has important theoretical significance and practical value for the design and application of seawater hydraulic components and systems.The main contents of this paper are as follows:(1)Using the fluid dynamics,lubrication and bionics theory and method,and basing on the working condition of the slipper pair in seawater axial piston pump,the relationship between seal gap and leakage flow is deduced,the best clearance between slipper and swash plate is calculated,a liquid film effect and dynamic lubrication model of bionic non-smooth surface with different shapes,sizes and distributions is established.This part of work lay the theoretical foundation for the numerical calculation of lubricating film bearing characteristics.(2)The liquid film effect and dynamic lubrication model of the above slipper pair with bionic non-smooth surface is calculated numerically by using the finite volume method in computational fluid dynamics.Then,through comparing with the velocity distribution,pressure distribution and bearing characteristics of the smooth surface slipper pair,the effect rule of the operating parameters(such as the film thickness and the rotation speed)and the geometric parameters(such as the shape,the size including the diameter and the depth to diameter ratio,and the distribution like the area ratio of the differential unit)on the lubricating film dynamic bearing characteristics is studied and investigated,and the lubrication and drag reduction mechanism of the bionic non-smooth surface is explored.(3)Based on the results of theoretical analysis and numerical simulation,316 L stainless steel and CF/PEEK are selected as matching materials to process several bionic non-smooth surface friction pairs with good dynamic bearing characteristics.Then the friction and wear tests under seawater lubricated condition are performed to investigate the friction and wear mechanism of friction pairs with bionic non-smooth surface.Through analyzing the parameters of friction coefficient,specimen temperature,wear rate and worn surface morphology of the bionic non-smooth surface friction pairs with different shapes of differential units under different working conditions,the friction and wear properties are explored.(4)Based on the results of numerical simulation and preliminary friction and wear test,several improvements are conducted such as exchanging the materials of the upper and the bottom specimen,modifying the structure of upper specimen,raising the rotation speed,and prolonging the test time.The purpose of all these improvements is to make the structure and working conditions of the friction pair closer to the actual situation of the slipper pair in the seawater axial piston pump.And then the influence of the diameters of bionic non-smooth units on its friction and wear properties is further explored.(5)Based on the above research results,taking a model of water axial piston pump as a prototype,the smooth surface swash plate is substituted with the bionic non-smooth surface swash plate made of 431 stainless steel.The property tests of the test pump are conducted on a water hydraulic test platform.The original and the worn surface morphology of the bionic non-smooth surface swash plate are compared and analyzed,and the volume efficiency and the mechanical efficiency of the test pump with bionic non-smooth surface slipper pair are investigated so as to verify the results of numerical simulation and friction and wear tests,and finally to provide valuable reference for the application of bionic non-smooth surface slipper pair in the seawater axial piston pump.