Virtual sensor of insufficient lubrication in variable speed compressors

Abstract

The ability to modulate the compressor’s speed and adapt the capacity to the load has permitted to decrease the annual energy consumption in many applications. However, in the compressor, having the correct lubrication at high speeds usually imply having insufficient lubrication at low speeds. This fact has to be considered by manufacturers as it limits the speed range of the compressor. In this study, a methodology to establish the working limit of a compressor is proposed. It is based on the specific consumption surface of the compressor and no oil circulation measurements are required. A compressor working between 6600 and 900rpm with propane and POE oil has been used to test the proposed methodology. The results show that lubricating issues in this compressor start at 1800rpm and rise as speed decreases.The authors would like to acknowledge the Spanish “MINISTERIO DE ECONOMIA Y COMPETITIVIDAD”, through the project ref- ENE2017-83665-C2-1-P “Maximización de la eficiencia y minimización del impacto ambiental de bombas de calor para la descarbonización de la calefacción/ acs en los edificios de consumo casi nulo” for the given support. In addition, Ruben Ossorio would like to thank the Spanish government for his PhD scholarship with reference PRE2018-083535