Characteristics Of Swash Plate Variable Displacement Compressor And Its Automotive Air Conditioning System

Variable displacement compressors (VDC) are more and more widely used in automotive air conditioning systems because of its benefit such as continuously steady regulation, better thermal comfort inside cars and less oil consumption. With the development of VDC, swash plate VDC (SPVDC), which have concise structures, finished designs, mature controls and reliable operations, are gradually replacing wobble plate VDC (WPVDC). However, there is no open publication which is deeply focused on the SPVDC and its refrigeration systems. In order to solve the problems of frosting in evaporators and system hunting in the practices, theoretical analysis and experimental investigation are combined to disclose the characteristics of SPVDC and its refrigeration systems.In the theoretical analysis: (1) The mathematical model of control valve is built based on the force analysis and conversation equations of mass and energy. (2) The dynamics model of movable components is built through the geometric, kinematical and force analysis. (3) The mathematical model of compression process is built through fitting experimental data. (4) Finally the steady state simulation model of SPVDC is finished based on the combination of the above three models. In the experimental investigations: (1) The methods and equipments are invented to measure the piston stroke and control valve of SPVDC. (2) The experimental systems and the piston stroke measuring equipment are combined to study the characteristics of SPVDC and automotive refrigeration system. (3) The simulation models are also validated by the test data.It is discovered by theoretical and experimental research that the "regulation dead zone" of the piston stroke is caused by the frictions among the movable components of SPVDC. The parameters are one-to-multi corresponding relationships during the changing process of the piston stroke, which is quite different from the one-to-one mapping relationship in constant piston stroke compressors. The influencing factors of the "regulation dead zone" include the rotary speed of compressor, the discharge pressure and the frictional factors. In the experiments, it is disclosed that (1) some system parameters such as the vaporizing pressure are also one-to-multi corresponding relationships because of "regulation dead zone"; (2) when the system parameters such as the car speed and the cooling load changes, SPVDC will automatically change its piston stroke to make the mass flow rate of refrigerant suit the cooling load; (3) the regulation process of SPVDC is so quick that its steady state model can be used for system dynamic performance analysis.The above-mentioned theoretical and experimental works of SPVDC and its refrigeration system can be the base of system designing, characteristics analysis and improvement.