3-D Transient CFD Model For A Rolling Piston Compressor With A Dynamic Reed Valve

Rolling pistons are widely used as compressors in air conditioning systems due to their small size, low cost, and high performance. Reed valves, a special type of check valve driven by hydraulic forces, are commonly used with many types of compressors to restrict the flow to one direction. Reed valves are typically made of a thin layer of metal or plastic materials. The valve will bend in response to fluid pressure forces to open up the flow channel at the proper moment within the compression cycle. There are many things that could affect the performance and efficiency of a compressing system. Among them, the interaction between the compressor and the control valves is one of the most important factors. Due to the fully coupled dynamic nature of the problem, analysis of compressor/valve interaction is difficult. CFD simulation of combined compressor and valve systems can provide valuable insights regarding not only the performance of the compressor and valve themselves, but also the critical dynamic interaction between the compressor and the valve. In this paper, a full 3D transient CFD model for a rolling piston compressor with reed valve is described in detail. In the proposed model, a moving/deforming mesh algorithm is developed for the fluid pockets of the rolling piston. The bending reed valve is modeled as a rotational structure with moving/deforming mesh for the affected fluid volume. The motion of the valve is solved using a one dimensional rotational ordinary differential equation. Based on bending cantilever beam theory, important parameters of the rotational dynamics, such as torsion constant, are carefully derived to accurately model the behavior of the bending reed valve. The meshing and re-meshing algorithms for the fluid volume of rolling piston and the rotational valve are implemented in the CFD solver PumpLinx. The test simulation of a real compressor and valve system demonstrates that the algorithms and the implementations are robust, fast, and user friendly, and can be readily applied to industrial rolling piston compressor systems