Abstract: To the scroll compressor with unit combined profile, the working characteristics of the whole machine is studied on condition that the vortex ring is modified by using symmetric circular arc.. The profile modification parameter equations are established. The data range of profile modification is discussed. The working characteristic of its working chamber, interior volume ratio and discharge area are analyzed. The results show that the scroll compressor with unit combined profile, in comparison with the one with normal circle involute profile, has larger discharge angle and discharge area under the same interior volume ratio, making the compression process more gently. And with the interior volume ratio increasing, the decrease trend of its discharge area is also slower than that of the compressor with normal circle involute profile. So, with the rise of compression ratio, the advantage of the scroll compressor with unit combined profile is more prominent. The study results lay a foundation for this novel scroll compressor applications and optimization.

Key words: Profile modification, Scroll compressor, Unit combined profile