The performance of a compressor changes during its lifetime, depending on various parameters such as operating conditions, type of the compressor, working fluid and type of the oil being used. Most performance degradation of the compressor is due to wear on the moving mechanical parts inside the compression vessel. Wear develops on the contact point(s) or area(s) between the moving and fixed mechanical parts inside the compressor when there is a lack of lubrication.
In a rolling piston rotary compressor, the most vulnerable regions are the vane and roller contact area, and the shaft and journal bearing area. As the amount of wear increases, leakage through the clearances inside the compression compartment increases as well. An increase in the amount of leakage degrades the volumetric efficiency and the overall performance of the compressor.
The objectives of this study are to predict the life span of rolling piston rotary-type compressors through the measurement of wear on the roller under accelerated test conditions, and predict the effect of wear on the degradation of compressor performance. In order to be able to estimate the amount of wear under different operating pressures, a correlation between operating pressures, amount of wear, and degradation of performance was developed. Then the change in compressor performance was estimated using a computer simulation program which takes into account the effect of leakage through the clearances inside the compression vessel based on the operating conditions provided.
One unit of rolling piston rotary type compressor was tested under accelerated operating conditions. An initial increase in the capacity and volumetric efficiency of the compressor was achieved due to aging affects. Then the performance of the compressor started to degrade due to increase in the amount of refrigerant leakage from suction pocket to discharge pocket of the compression compartment.
Source: University of Maryland
Author: Layla Monajemi