Investigation of oil-injected screw compressors performance based on energy efficiency and pressurized air quality

Energy consumption of a compressor can constitute almost 40% of the overall energy consumption of a facility. Screw compressors are the most common type of compressors. The main function of the bare screw compressor is to pressurize gas. While the gas is being compressed in a pressure chamber of an oil injected screw compressor, gas temperature causes entropy generation. So, some oil is injected into the pressure chamber as a coolant. This oil injection also provides lubrication for rotors and decreases leakages. This study covers the calculation of oil injection port locations and injection nozzle diameters based on the cooling effects of oil on air. This study also investigates hydrocyclone performance of an oil injected screw compressor. Hydrocyclones cover a significant portion of overall energy performance and the oil separation efficiency of a screw compressor is significant for air quality. As a result of their complex flow structure they cannot be modelled with algebraic methods. Therefore, numerical CFD methods are preferred for the purpose of the estimation of hydrocyclone flow. Modelling a hydrocyclone with CFD needs more extended study compared to modelling a cyclone. In this study, three separation efficiency parameters of hydrocyclone are investigated, i.e., vortex finder location, inlet diameter and flow volume height between oil reservoir surface and top of the hydrocyclone. With regard to separation and energy performance, thirteen different cases have been investigated which are cyclone inlet diameter and flow volume height between oil reservoir surface and top surface of oil. The reversed vortex generation was observed at various cross-sectional planes of flow volume of the tank. The inlet diameter of the cyclone proved to be related to the centrifugal force on particles, so decrease in diameter means faster inflow; and a larger diameter implies slower inflow. On the contrary, increment in the flow speed causes breakup problems, causing the particle diameters to get smaller; consequently, separating particles from gas becomes harder.