Research On Flow Characteristics Of The Rolling Piston Compressors With Dynamics Mesh Method

Rolling piston compressors are widely used in the fields of household air conditioners and refrigerators. China has become the manufacturing and leading research base of the rolling piston compressors. With the emergence of the world-wide energy crisis, the deterioration of the climate and requirements for comfort degree, how to improve the efficiency and to reduce the noise of the compressors has become an important researching subject for the engineers. This dissertation focuses on the physical processes and phenomena of the refrigerant flow in the compressor. It establishes a compressible turbulent flow model in the complex flow region of the pump chamber and the accumulator by using the software of ANSYS-CFX CFD (computational fluid dynamics) platform through controlling the grid node coordinates of the deformation space. Moreover, the simulation of the refrigerant fluctuation phenomenon is realized by DES (detached eddy simulation) method. The comparison of the numerical results with the experimental data proves the reliability of the as-built method and model.The study indcates that the pressure disturbance is produced in the process of gas compression in the pump chamber by the rotor, and phenomena such as shocks and vortex flow generate when the pressure fluctuations spread in the flow space. Hindered or affected by the geometric space, the vortex flow is formed at the bottom of the compression chamber or region near the vane wall, which is the main fluid noise source. In addition, the pressure gradient of the exhaust chamber points to the vent in the exhaust process. The pressure is higher at the bottom of the chamber than that of the other regions. The analysis shows that the shape, size, especially the location of the vent have a significant impact on the vortex flow of the compression process and the pressure gradient of the exhaust process.This work also analyzes the flow process in the accumulator. The periodic pressure fluctuation is produced by the periodic volume change rate of the pump chamber and the flow resistance in the accumulator. The essence of the pressure fluctuation is the transformation between the potential energy and the kinetic energy. The flow resistance greatly affects the periodic pressure fluctuation and the volumetric efficiency. It is one of the factors to improve the volumetric efficiency of the compressor. But the flow loss mainly happens in the energy conversion processes. The effect of the flow resistance on the indicated efficiency can be neglected as compared with that of the other factors such as wall heating.A vent structure with a smaller loss of the clearance volume and the flow than that of the existing structures is proposed in this work based on the flow characteristics of the compressor. The numerical results support that this structure remarkably improves the compressor efficiency and reduces the fluid noise.In this work, the phenomena in the flow process such as clearance leakage, expansion flow of the gas in the clearance volume, reflow of the inlet, the temperature distribution of the suction chamber, the turbulent eddy distribution are alsostudied. Although some aspects need to be improved and modified, the current study has practical significance for improving the researches and the performance of the rolling piston compressor.