An Analytical Study of the Oil Supply System in Scroll Compressors

This Paper has studied the oil supply characteristics to scroll compressors for package air conditioners. Scroll compressor has four major lubricating parts: the lower journal bearing, the main journal bearing, the orbiting scroll journal bearing and the thrust bearing between the orbiting scroll and the main frame. It is very important to supply the required flow rate of oil in order to prevent these lubricating parts from wearing. Namely if the required flow rate were not supplied to these lubrication parts, the locking phenomena of scroll compressors would frequently occur. So we had to study the characteristics of the oil supply system for the reliability of scroll compressors. In this study we estimated theoretically the supply flow rate, pressures, resistance and the required flow rate according to several design parameters of the oil supply system. In this simulation equivalent electrical circuit was used, and we compared these results with the experimental data in order to improve the accuracy of simulation. Parameter B Oil Groove Width C Clearance , Coefficient D Diameter H Oil Groove Height, Oil Film Thickness N revolution P Pressure Q Flow Rate R Radius , Resistance , Roughness T Temperature NOMENCLATURE Subscript gc Rotational Flow of Oil groove gp Pressure Difference of Oil Groove Without Rotation m Minimum Oil Film Thickness n Necessary Flow Rate o Orifice p Pressure Difference Flow r Rotation s Leakage Flow INTRODUCTION Greek /3 Groove Angle e Eccentric Ratio A Oil Film Parameter fl. Viscosity ~ Shape Coefficient K Pi p Density (J) Angular Velocity Scroll compressor is consisted of a motor, a shaft, :fiXed and orbiting scrolls, and main and lower frames that support the shaft. It is superior to rotary and reciprocating type compressors in efficiency, noise and vibration due to its structural advantages. But it is rather difficult to supply enough oil to the lubricating parts because these parts are located at the upside of compressor. So it is much more important to supply oil properly to these parts in term of reliability. Oil plays important roles in compressors, such as the prevention of gas leakage at the compression chamber, the lubrication of the lubricating parts and the cooling of the lubricating parts heated by friction heat. If oil is oversupplied to the lubricating parts, the oil discharged into cycle increases. The poor supply of oil results in the temperature rise of bearings. So it is required to design the optimum oil supply system to guarantee high reliability and efficiency of scroll compressors. Until now many studies about the oil supply system of scroll compressors have been done, but only few take the whole system as an object of analysis. In this study, we take into accounting the whole oil supply system and we are to design the reliable oil supply system that the supply flow rate can satisfy the required flow rate for the lubrication and the cooling of the lubricating parts.