Investigation on the Each Stage Pressure Ratio and Valve Dynamic Characteristics in Multistage Compressor

The each stage pressure ratio and the dynamic characteristics of valves are key factors affecting the performance of high-pressure multi-stage reciprocating compressors. This paper established a thermodynamic model for a 3-stage compressor, and analyzed the effect of the discharge pressure, cylinder diameter, and clearance volume in each stage on the 3-stage pressure ratio distribution, and obtains the optimal pressure ratio distribution. Using the optimal pressure ratio distribution as the boundary condition, the fluid-structure interaction (FSI) numerical model for cylinder in each stage were established, and the influence of valve stiffness on dynamic characteristics of valve and the field distribution in valve gap were analyzed. The results indicate that the first and second stage pressure ratios are mainly controlled by the volume ratio, and are not significantly affected by the discharge pressure. The mass flow rate obtained by the FSI model of cylinder in each stage is approximately equal, indicating that the pressure ratio distribution calculated based on the thermodynamic model can serve as a boundary condition for the FSI numerical model. This paper provides a theoretical basis for the design method of the multi-stage compressors.