Analytical model for a 10 cylinder swash plate electric compressor

Abstract

Recent advancements in the field of mobile air conditioning and refrigeration have witnessed an extensive use of the swash plate compressor due to its compact structure, continuous operation, small size, light weight and better thermal comfort inside the vehicle. The design of the swash plate compressor is complex so that it requires considerable contributions from different fields of engineering viz. engineering mechanics, heat transfer and fluid dynamics. An estimate of compressor performance through an analytical/ mathematical model at the early stages of design and development serves as a useful tool for the designer. The input power, refrigerant mass flow rate, compression ratio and volumetric efficiency are important parameters to characterise the compressor performance. This paper presents an analytical/mathematical model for a 10-cylinder swash plate compressor with the emphasis on predicting its performance in terms of shaft torque and mass flow rate for a given rpm. A kinematic model is developed to obtain the piston displacement as an explicit function of angle of rotation of the swash plate. The model of piston and swash plate dynamics is developed then by analysing the interactions between forces and moments. The compression process model is formulated to determine the temperature and pressure inside the cylinder during one revolution of the swash plate along with the total mass flow rate in and out of the compressor. A time-varying model for the compressor is developed by combining the above three sub-models. Some experimental validation comparing predicted and measured drive torque has been done to verify the analytical/ mathematical model The predicted torque is in close agreement with the measured value.