Investigation of flow behaviour and heat rejection for an air-cooled small multi-stage swash-plate compressor

Modelling the working process of a multi-stage reciprocating compressor is essential for improved performance and reliability. However, the squeeze-like thermal flows in the cylinder and valve plate-seat chamber, and their interactions with the inter-stage and exterior cooling flows, are so complex that detailed treatments of interactions with the surrounding environment have yet to be reported. To facilitate real-environment modelling, a numerical method is proposed within the framework of a multi-physics computational fluid dynamics package by incorporating a squeeze-like dynamic mesh and the fluid-structure interaction. With the developed approach, a three-stage four-cylinder compressor is simulated, where the valve dynamics, cylinder head heat rejection mechanism, and interior and exterior thermal-flow behaviour are exhibited. The results showed that the maximum impact velocity of the Stage 1 discharge valve is 4.8 times larger than that of the suction valve, which means that the Stage 1 discharge valve is more prone to fatigue damage. The suction air temperature is superheated owing to the heating of the cylinder head, which reduces the compressor volumetric efficiency and increases the compressor work. The predicted outer surface temperature of the cylinder head is comparable to the experimentally measured value, with a deviation of less than 6.9%, thus verifying the proposed method.