Effects of Surface Roughness upon Gas Leakage Flow through Small Clearances in CO_2 Scroll Compressors

摘要

This study presents empirical values of the friction factor for CO_2 gas leakage through thin rectangular cross-sectional openings of small axial and radial clearances between the orbiting and fixed scrolls of scroll compressors. Leakage flow experiments are conducted for different relative roughness of leakage channel surface. The pressure drop due to leakage is measured using a maximum pressure of 3 MPa. The Darcy-Weisbach equation for incompressible, viscous fluid flow through the thin rectangular cross-section is applied to calculate the pressure drop characteristics, where the empirical friction factors are determined and plotted on a Moody diagram. As a result, it is shown that the empirical friction factors for both axial and radial clearance leakage flows take on essentially the same values, strongly dependent on the relative roughness of leakage channel surface. Subsequently, the empirical friction factor is incorporated into computer simulations for a CO_2 scroll compressor with small cooling capacity to determine its optimal performance. As a result, it is shown that CO_2 scroll compressors can achieve higher performance levels by increasing the relative roughness of scroll wrap surfaces.