Numerical Analysis Of Lubrication Properties Of Thrust Bearing At Low-side Scroll Compressor

The strengthening effects of growing energy crisis and the growing global warming trend are profoundly changing people's lifestyles,and people are gradually aware of the importance of saving energy and reducing energy consumption to improve the earth's ecological environment.As a new kind of positive displacement refrigeration compressor,the scroll compressor has attracted widespread concern with its high efficiency,low noise,smooth operation as well as the simple structure.The scroll compressor first appeared on the commercial air conditioning market in 1983,since then,research on the performance of scroll compressors has been extensive and deep during the short 30 s.In the scroll compressor,the thrust bearing is mainly used to balance the axial force of compressed refrigerate pressing the orbiting scroll downward,it has been widely employed in a variety of size of the compressors because of its excellent load-carry capability and low fractional characteristics,which are very contributing factors for the compressor to exhibit superior performance and efficiency.The thrust bearing at the low-side scroll compressor is composed of two thrust surfaces,one is the back surface of the orbiting surface,the other is the step surface of the main frame.During the orbiting motion of the orbiting scroll,the tangential force,the radial gas force and the centrifugal force generated by the eccentricity orbiting movement are not co-planar with driving surface of the orbiting scroll,as a result,a tilting moment is formed to cause the orbiting scroll's wobbling motion.The tilting of orbiting scroll can provide essential conditions for the thrust bearing to produce hydrodynamic lubrication,for instance,geometric wedge can provide the hydrodynamic effects,at the same time,hydrodynamic oil film can effectively balance the axial force.Above all,study on the lubrication theory of the thrust bearing is necessary.In this paper,we mainly study the lubrication performance of the thrust bearing due to the tilting of the orbiting scroll which is induced by the tilting moment.First of all,numerical methods are used to solve the Reynolds equation and find the apposite values to satisfy balancing in both force and moments between the calculated hydrodynamic pressure and a given input of the axial force and its locus,which is based on the analysis of the thrust force and the overturning moment and the establishment of the fluid lubrication equation.In one revolution,the oil film pressure distribution and the oil film thickness distribution of the thrust bearing are analyzed,besides,the changes of oil film thickness,tilting angle of the orbiting scroll and directional angle of the tilting are also studied.On this basis,the effect of main shaft speed on lubrication properties is studied,and the effect of the radial position of the thrust force at the thrust bearing on the generation of hydrodynamic oil film is focused.The results are as follows: the oil film pressure distribute mainly at areas where the orbiting tilt,and a ‘U' shape is formed.In one revolution,the U shape oil film pressure is formed alternately at different position at the thrust bearing,which shows the lubricant can flow easily in the circular oil groove set up on the thrust bearing,as a result,this can decrease the lubricant leakage.In addition,the max oil film pressure,oil film thickness at the center of the orbiting scroll and the tilting angle change little in one revolution.Second,the formation of hydrodynamic oil film limit in a finite areas when the position of the thrust force at the the thrust bearing changes at the radial direction.The numerical solution can't be obtained when the radial position exceed the limit range,which maybe cause unwanted bearing behavior like metal contact metal,wear,or mechanical instability.At last,the optimized design of the scroll compressor is conducted to improve the lubrication properties of the thrust bearing.