Theoretical and Experimental Studies on Oil Injected Twin Screw Air Compressor under Unload Conditions

Abstract

The working process of twin screw air compressor under unload conditions was analyzed. Mathematical model describing the working process of oil injected twin screw compressor under unload conditions was established based on the laws of perfect gas and standard thermodynamic relations, considering the effects of oil injection, gas-oil heat transfer, internal leakage etc. A simulation model of screw air compressor system based on MATLAB was built up, and the effects of rotational speed and discharge pressure etc. on the performance under unload conditions were analyzed. The experiment was carried out to validate the model by a comparison between the results of the simulation model and testing. The simulation and testing results both showed that volumetric efficiency increased with the increase of rotational speed, when the discharge pressure was reduced. The shaft power increased with the increase of discharge pressure and rotational speed. The flow rate increased with the reduction of discharge pressure and increase of rotational speed. This model can be used for performance prediction under unload conditions and it provided reference for the high efficiency and energy saving operation of screw compressors.