Study On Radial Leakage Characteristics Of Rolling Piston Compressor

Leakage is a major factor affecting the volumetric efficiency of the compressor,and the compressor mainly stops the leakage of gaseous refrigerant through the lubricant film.Among the four main leakage channels of compressor,radial clearance leakage is the most prominent,and its leakage proportion is the largest.Therefore,it is positive and practical significance to explore the radial clearance leakage characteristics of compressor.At present,there are mainly two methods for the study of the radial clearance leakage characteristics:ignore the effects of lubricant film under dynamic pressure conditions,and only consider single-phase flow of gaseous refrigerant leakage;the size of the lubricating oil film is regarded as a fixed value under the static pressure conditions,and the gas-liquid two-phase flow affected by the leakage of the lubricating oil film to the gaseous working fluid is considered.However,with the operation of the compressor,the pressure in the chamber and the size of the oil film in the radial clearance are constantly changing.Therefore,there is still a certain clearance between the above research methods and the actual operating conditions of the radial leakage passage of the compressor.In this paper,a fully enclosed single-stage vertical rolling piston compressor is studied.The CFD is used to simulate the gas-liquid two-phase flow under dynamic pressure difference.The change law of the sealing angle of the oil film and the leakage characteristics of the radial clearance under the influences of the rotating speed,the radial clearance,the viscosity of the lubricant and the thickness of the oil film are obtained.Experiments are carried out based on CFD simulation and the leakage characteristics of gaseous materials under the influence of rotating speed,radial clearance,lubricating oil viscosity and sealing Angle of oil film are obtained.Finally,the flow field characteristics of compressor cavity are obtained by establishing 3D simulation model.The research content of this paper is as follows:(1)The oil film seal angle is simulated,obtained the size and variation law of the oil film seal angle,the results show that there is a positive correlation between rotating speed,lubricating oil adhesion thickness and sealing angle of oil film in the absence of pressure difference,and a negative correlation between lubricating oil viscosity and sealing angle of oil film.Under dynamic pressure difference,the oil film sealing angle disappears when the piston rotation angle is about 45° and forms at 120°.The lubricating oil adhesion thickness is positively correlated with the oil film sealing angle.The lubricating oil viscosity,radial clearance and the oil film sealing angle are negatively correlated.When the piston angle is 45°-60°,the rotation speed is negatively correlated with the sealing angle of the oil film;when the piston rotation angle is 60°-120°,the rotation speed is positively correlated with the oil seal angle.(2)Through the oil film sealing angle observation experiment,MATLAB is used to process pictures taken by high-speed photography,and the influence of the three factors without pressure difference on the sealing angle of the oil film is obtained.Comparing the simulation data without pressure difference with the experimental data,the results show that the error between experimental data and simulation data is less than 20%,and the simulation method used is reasonable.(3)The leakage characteristics of radial clearance are simulated.The results show when the volume loss is less than 5%,the rotation speed should not be less than 3000r/min,the clearance should not be larger than 45μm,and the adhesion thickness of the lubricating oil on the piston wall should not be less than 50μm.The influence of the viscosity of the lubricant is small and may not be considered.(4)By acquiring dynamic pressure on the compressor body.The radial clearance equivalent device is used to simulate the radial clearance of the compressor,and the gas leaked from the equivalent device is collected and measured by the observation device.Through image processing,the influences of four factors,such as rotation speed,lubricating oil viscosity,oil film sealing angle,and radial clearance,on the leakage characteristics of radial clearance are obtained.The results show that the influence of the four factors on the leakage rate is consistent with the simulation results,and the leakage volume increases logarithmically when the equivalent radial gap gas leaks.(5)A 3D simulation model of the cavity is established.Simulation results show before the compressor exhaust,oil is concentrated in the radial clearance,negative pressure will appear on the side of the radial gap near the suction chamber.The flow line in the compressed cavity is basically consistent and spiral in the direction of the axial compression cavity.The vortex is produced at the position of the vent,and the temperature distribution in the compression cavity is uneven;the pressure of the suction chamber is small and the flow field is steady.The distribution of the fixed and temperature is uniform.