Analysis of oil pumping in a reciprocating compressor

The immediate provision of lubricant oil to the radial and thrust bearings and to the piston–cylinder gap in reciprocating refrigeration compressors is a crucial reliability issue following compressor start-up. The aim of this paper is to present a hydrodynamic analysis of the lubricant oil pumping system of a reciprocating compressor using computational fluid dynamics (CFD). In the present system, oil is pumped from the sump through a reed-type centrifugal pump located at the bottom end of the shaft. The oil flows initially as a climbing film on the internal surface of the shaft before it is directed to the external surface where it flows along a helix channel carved on the shaft wall. The model was implemented on the commercial package Fluent using the volume of fluid (VOF) method to resolve the free-surface oil flow. Parameters regarding the oil behavior during start-up, such as the time required to reach steady-state operation and the associated oil mass flow rate are explored in the manuscript.