Numerical analysis of a miniature multi-stage compressor at variable altitudes based on stages-in-series method

Oil-free miniature multi-stage compressor (MMSC) is significant for delivering clean compressed air to mobile applications, and its thermodynamic performance can be greatly influenced by environmental factors. In this research, a stages-in-series numerical model for the multi-stage swash-plate compressor was established by comprehensively considering the real-time variations of gas properties in the intercooler flow channels. On this basis, the thermodynamic performance of the compressor at variable altitudes with different environmental characteristics was studied numerically. The results showed that the volume flow rate of the compressor de-creases nonlinearly as the altitude increases. With each 2000 m increase in altitude, the total indicated power required by the compressor reduces by approximately 19 %. The volumetric efficiency of the first, second and third stage cylinder decreased by 0.86 %, 4.01 %, and 9.41 % on average, respectively, which means that the 3rd stage cylinder is the least suitable for high altitudes.