A Fundamental Optimum Design for High Mechanical and Volumetric Efficiency of Compact Rotary Compressors

Abstract

This paper presents a fundamental optimum design which yields a high compressor performance in mechanical and volumetric efficiency of a rolling-piston rotary compressor. The frictional power losses at each pair of machine elements were calculated by an analytical method revealing the dynamic behavior of rolling-piston rotary compressors, and the refrigerant leakage from axial and radial clearances was calculated by the incompressible and viscous theory assuming an entire turbulent leakage flow. Computer calculations were made for a number of combinations of the major dimensions for various suction volumes. Calculations for the mechanical and volumetric efficiency resulted in an optimum combination of major dimensions for various suction volumes of the rotary compressor. INTRODUCTION The suction volume of rolling-piston type rotary compressors is determined on the basis of the major dimensions, such as the rolling-piston diameter, the cylinder depth and the cylinder bore. It becomes clear that there are many combinations of the major dimensions that yield a rollingpiston rotary compressor with the same suction volume. Depending upon the combination of the major dimensions, the constraint force at each pair of the compressor elements changes and as a result the power loss due to mechanical friction changes. Based on such viewpoint, the mechanical efficiency was calculated for various combinations of the major dimensions to present an optimum combination chart diagram which yields a high perfmmance in mechanical efficiency, by Ishii et al. (1990 /1!). Similar calculations have been made for scroll compressors by Ishii et al. (1990 /2/; 1992 /3/; 1994 141). In addition to the mechanical efficiency, the volumetric efficiency also has to be calculated, since the leakage flow path area between the compressor elements changes depending upon the combination of the major dimensions. For the scroll compressors, a simple method to evaluate refrigerant leakage flows through the axial and radial clearances between scroll compressor