Abstract: The scroll compressor’s radial labyrinth sealing is regarded as the research object, by using the macro energy method and the theory of viscous flow, the leakage for the sealing structure are calculated, to find aerodynamic and thermodynamic behavior of gas leakage. A comparison is made between experimental results and theoretical predictions. Assuming that there is no ventilation effect and the gas do isobaric and isothermal recovery in the labyrinth groove, the mathematical equation of leakage is established; while considering the ventilation effect and non isobaric isothermal recovery, by using thermodynamic equation and the theory of viscous flow, discriminant for judging whether ventilation flow comes up to speed of sound is deduced, and the algorithm to calculate critical velocity, critical density and leakage is proposed. The different between experimental results and theoretical predictions of leakage is analyzed. The result indicates that leakage process in straight through labyrinth sealing is expansion process accompanied with absorption of heat. The thermodynamics index decrease obviously with the increase of the pressure differences of two adjoining pressure chamber, and the leakages is composed of ventilation flow and 2D Poiseuille between in adjoining labyrinth groove, ventilation effect become also clearer with the increase of the pressure differences. The algorithm with theory of viscous flow for leakage has high computational precision.

Key words: leakage, Poiseuille flow, radial labyrinth, scroll compressor, ventilation flow