Abstract: In this paper, the trilobal Roots pump is taken as the research object, starting from its basic structure and working principle, its internal gas transport process was analyzed thermodynamically. Taking the gas as the research object, the time sequence analysis was carried out, and the process of the gas in the pump was decomposed into intake, transport, recoil, discharge, and discussing the characteristics and mechanism of each stage in detail. The knowledge of thermodynamics and the amount of backflow were taken into account. Calculating gas backflow through model. The quantitative analysis of each phase was carried out, and the time-variation formulas of thermodynamic parameters were deduced, such as pressure, volume, mass, and internal energy. The formula was used to explore the relationship between exhaust power and import and export pressure.

Key words: Three-lobe Roots vacuum pump, Thermodynamic process, Analytical calculation, Time sequence analysis