| High pressure and large displacement radial piston pump has the advantages of high working pressure,shock resistance,long service life,low noise and high control precision,which is widely used in the hydraulic system of metallurgical,mining,forging and other mechanical equipment.In particular,the hydraulic syst em of super ten thousand ton pressure machine and the hydraulic wind power generation system must use high pressure and large displacement radial piston pump.However,there are some problems in the high pressure and large displacement radial piston pump,such as inaccurate calculation of instantaneous flow,insufficient understanding of dynamic characteristics of slipper pair and insufficient design basis,which lead to the highest failure rate of slipper pair among the three friction pairs.At present,hi gh pressure and large displacement radial piston pumps are mostly produced in small batch and mainly rely on imports,so the price and maintenance costs are very high.The research on instantaneous flow and dynamic characteristics of slipper pair of high p ressure and large displacement radial piston pump will provide basic theoretical support for optimizing design theory of the pump,improving reliability and prolonging service life.Aiming at the problem of slipper pair friction failure of XDP1000 high pressure and large displacement radial piston pump(the rated pressure is 42 MPa,the displacement is 1000 m L/r),considering the compressibility of oil,the change of oil pre-compression pressure and instantaneous flow calculation and its influencing factors are studied.Then,the oil film thickness equation of slipper pair is established,and the flow field numerical simulation and fluid-solid-thermal coupling analysis are carried out to obtain the distribution characteristics of pressure,temperature and deformation of oil film of slipper pair.The main work and conclusions are listed as follows:Firstly,the motion parameters of large displacement radial piston pump are analyzed and calculated.The error analysis of the displacement,velocity and acceleration of the piston obtained by the approximate calculation method shows that there are large errors in the above parameters and the error variation rules are also different.The calculation formula of motion parameters based on coordinate method is put forward,and the result is exactly the same as that of accurate calculation.According to the special installation form of the stator,the motion mechanism diagram is constructed for analysis,and it is found that the stator will move at a variable angular velocity under the action of different position slippers.The pre-compression curves of the oil in the piston cavity are obtained through the calculation of the mathematical model and the computational fluid dynamics(CFD)model when considering the compressibility of the oil.The shape of the two curves is similar,and the pressure obtained by CFD model is slightly higher than that of the mathematical model.The calculation formula of the actual instantaneous flow of the pump is established,and the curve of the instantaneous flow is obtained.The influence of the working condition parameters and the structural parameters of the damping groove on the actual instantaneous flow is discussed.After the results of the pre-compression of the piston cavity are obtained,the calculation model of the oil film thickness of the slipper pair of the large displacement radial piston pump is established.It is found that the oil film thickness of the slipper pair in the oil discharge area is not constant and changes from small to large.When the working pressure of the pump is constant,the oil film thickness increases with the increase of the rotation speed.When the rotation speed is constant,the oil film thickness of the slipper pair decreases with the increase of the working pressure.The difference between the two values is large,and the influence of working pressure and rotation speed is opposite.Then,through the numerical simulation of the flow field,it is found that the most high pressure area of the fluid domain of the slipper pair is located in the central oil cavity,and the low-pressure area and the high pressure area are appeared in the front and rear sides of the central oil cavity respectively.The pressure field in fluid domain of slipper pair increases obviously with the increase of pump working pressure,and basically remains unchanged with the increase of pump rotation speed.The high speed area of the oil film is the wall near the stator side,and the high temperature area is located in the oil film area of the slipper pair.The distribution of velocity field and temperature field is not affected by working pressure,but by pump rotation speed.Further analysis of the influence of pressure field and temperature field on the slipper structure shows that the temperature distribution of the slipper structure is basically consistent with the fluid domain,and the high temperature area is mainly concentrated on the bottom of the slipper which contacts with the oil film,and gradually decreases from the surrounding of the bottom to the center of the central oil cavity.The maximum stress and deformation of the slipper is located in the outlet edge of the damping hole at the bottom of the central oil cavity.It is found that the local stress of the slipper structure increases greatly when considering the thermal load.Finally,the tribological characteristics of slipper material of high p ressure and large displacement radial piston pump are studied.The GCr15 and 20 Cr Ni Mo are used for the stator materials,and the bronze,sintered copper and nonmetallic materials are used for the slipper materials.The movement form of the test ring and test block is consistent with that of the stator and slipper of the pump.Through the analysis of friction coefficient curve,wear rate and friction morphology,it is found ZQSn10-2-3and other four materials have better stability,and smaller friction coefficient and wear rate,which can be used as the material of slipper. |
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