| The lubricating oil film at the radial clearance of the rolling piston compressor acts as the lubrication of the cylinder block and the working surface of the rolling piston in the radial clearance,and also has a certain sealing effect on the high pressure gas leaking from the high pressure chamber to the low pressure chamber.It is of great practical significance to study the lubricating performance and sealing performance of lubricating oil at radial.clearance.At present,there are many researches on the leakage of the radial clearance of rolling piston compressor at home and abroad,and the research methods used are relatively rich,such as theoretical research,experimental research and simulation research,etc.However,there are few researcheson lubricating performance and sealing performance of lubricating oil film at radial clearance,so it is necessary to study lubricating performance and sealing performance of lubricating oil film at radial clearance.At the same time,the multi-objective optimization of lubricating oil film and sealing performance at radial clearance can play a certain guiding role in engineering design.The main work and research contents of this paper include the following aspects:(1)The pressure and volume of the two working chambers of the rolling piston compressor are simulated and the pressure curve of the working chamber is obtained.At the same time,the motion law of the rolling piston is analyzed,and the rotation angular velocity of the rolling piston is obtained.(2)According to the hydrodynamic lubrication theory and the hydrodynamic lubrication theory of radial sliding bearing,the Reynolds equation of lubricating oil film at the radial clearance between rolling piston and cylinder block is established.The viscosity model and density model of lubricating oil at radial clearance in two-phase flow state were analyzed and the two-phase flow Reynolds equation of radial clearance lubricant film was established.(3)By setting up an equivalent test platform and controlling rotor speed,rotor radius and lubricating oil viscosity,The operating state of lubricating oil film with radial clearance and the rupture and reformation of lubricating oil film after passing through the minimum gap of radial clearance were obtained under different experimental conditions.The angle of oil film seal at radial clearance is observed,the boundary conditions of Reynolds equation are obtained,and the calculated value of seal angle of oil film is obtained by solving the Reynolds equation of two-phase flow.The results show that the oil film seal angle can be calculated by solving the two-phase flow Reynolds equation.The relative error between the experimental and theoretical values of oil film sealing angle is within 4.58%.(4)Under the boundary condition that the hole pressure is equal to the ambient pressure,the five-point difference method is used to solve the two-phase flow Reynolds equation,and the mesh independence test is carried out in the calculation process.The results show that the calculation results when the mesh number is 70 are taken as the benchmark.The relative error between the calculated results of friction,oil film stiffness and friction and other meshes is within 1%.However,the relative error between the calculation results of oil film seal angle is slightly larger,about 3%.By changing the minimum clearance value of radial clearance,the dynamic viscosity of lubricating oil and the different pressure distribution of rotor speed,the effects of radial clearance,viscosity of lubricating oil and rotational speed of rotor on the sealing performance and friction force of lubricating oil film were studied.The curves of seal performance and friction force of lubricating oil film with different rotational speed,lubricating oil viscosity,radial clearance and lubricating oil film are plotted.The results show that the oil film seal angle increases with the increase of rotational speed and the dynamic viscosity of lubricating oil,and decreases with the increase of minimum clearance value,but has little effect on the oil film seal angle under the condition of the same oil intake in each circle of eccentric axis rotation,but the oil film seal angle increases with the increase of rotational speed and the dynamic viscosity of lubricating oil.In the calculation range,the oil film seal angle is within 2.4°,and the oil film seal angle is between 21.6°and 24°.At the same time the oil film seal angle decreases with the increase of the dynamic viscosity rotational speed and minimum clearance value of the lubricating oil.At the same time,the rotational speed has the most significant effect on the oil film seal angle at the radial clearance.In thecalculation range,the variation range of the oil film seal angle is 16.3°to 40.2° under the influence of the rotational speed.However,the influence of the minimum clearance at the radial clearance and the viscosity of the lubricating oil on it is much smaller.In the calculation range,the oil film seal angle caused only by the minimum clearance at the radial clearance or the viscosity of the lubricating oil is within 2°.When the minimum clearance value is less than 30 μm and the dynamic viscosity of lubricating oil is not less than 40.1mPa s,the oil film bearing capacity,film stiffness and friction force increase with the increase of rotational speed.When the minimum clearance value is more than 30 μm and the dynamic viscosity of lubricating oil is less than 40.1mPa s,the oil film bearing capacity,film stiffness and friction force decrease first and then increase with the increase of rotational speed due to the decrease of oil film seal angle.The oil film bearing capacity,film stiffness and friction force increase with the increase of the dynamic viscosity of the lubricating oil,and decrease with the increase of the minimum clearance value.In the case of the same oil intake in each circle of eccentric axis rotation,the oil film bearing capacity,film stiffness and friction force increase with the increase of rotational speed and the dynamic viscosity of lubricating oil,and decrease with the increase of minimum clearance value.(5)In order to improve the sealing performance of the lubricating oil film at the compression and radial clearance of the rolling piston and reduce the friction of the lubricating oil film,the optimal solution set is obtained by using the multi-objective optimization algorithm(NSGA-II).The results show that,in the calculation range,only the multi-objective optimization of the oil film bearing capacity,the oil inlet quantity and the friction force is considered,and at the same time,the front angle of the oil film at the radial clearance is kept at 20 degrees,the speed and the lubricating power viscosity should be taken as large as the speed is close to 3000RPM,The dynamic viscosity of the lubricating oil is close to 89.3mPa-s;while the minimum clearance,value at the radial gap should be smaller and better,that is,the minimum clearance value is close to 30μm. |
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