This paper was produced for the 2019 NAFEMS World Congress in Quebec Canada

Resource Abstract

The main demands for the industry of commercial and household refrigeration appliances are: eco-friendly, lower power consumption, better performance, finer temperature control and lower noise levels. One example into this direction is the innovating variable speed compressors – a component of the refrigeration system – gaining space in the market due to the benefits which they bring. The variable speed compressor differs from the conventional compressor in adjusting the rotational speed according to the refrigeration system’s demand. This is achieved by the presence of an electronic device – the frequency inverter – capable of measuring the temperature variations of the system and automatically adjusting the compressor speed, making the operation more efficient.



When a compressor works at different speeds all its components need to be designed to operate under these conditions. One fundamental function of the compressor cranktrain is ensuring proper lubrication for the mechanical components. For this purpose, the cranktrain’s oil pump system must perform such function. In the last decade, techniques of physical and computational experiments have aided the robust design of the oil pumping system, optimizing the oil flow rate for a wide range of crankshaft speeds.



Through computational and physical experiments, this study aims to analyse simplified simulation models for the centrifugal oil pump system of reciprocating compressors. The numerical method solves the biphasic and immiscible fluid flow from the homogeneous free surface model. The main response variables are: a) the volumetric oil flow rate; b) the oil volume fractions; c) the oil velocity fields; and d) pressure fields. The study evaluates three numerical models: a) the full model; b) the simplified model 1; and c) the simplified model 2. The full model considers the full domain of the oil pumping system; the simplified model 1 neglects the crankshaft grooves from full domain; lastly, the simplified model 2 neglects both the crankshaft grooves and the oil sump from full domain. The numerical results have shown that both simplified models overestimate the oil flow rate; the better agreement with experimental data was achieved with the full numerical model.