Abstract: A kind of radial labyrinth for scroll compressor’s radial sealing is presented. By using geometric and thermodynamic method, the velocity of gas in radial sealing with smooth clearance of circumferential involute scroll compressor is determined as speed of sound, thermodynamic vary of gas in radial sealing with smooth clearance is analyzed, on the basis of the thermodynamic and boundary particularities, the algorithm to calculate the leakage through radial sealing with smooth clearance is developed, according to the law of the conservation of energy and mass, discriminant for judging whether the velocity of gas in radial labyrinth comes up to speed of sound is deduced, and the algorithm to calculate the leakage through radial labyrinth is also deduced. The leakage under the different pressure differences of the two adjoining pressure chambers are obtained by calculation and experiment. The results show that the algorithms for the leakages of the two kinds of structures are correct, with the increase of the pressure differences of the two adjoining pressure chambers, the leakages of the two kinds of structures become large, and the straightforward leak effect of radial labyrinth become clear, the ratio of the experimental leakage of the radial labyrinth accounts for that of the radial sealing with smooth clearance is practically constant at about 79%，it shows that the radial labyrinth has better sealing performance compared with the radial sealing with smooth clearance.

Key words: Leakage, Pressure difference, Radial labyrinth, Scroll compressor, Sealing performance