Performance of oil-free scroll-type air compressors

The performance of oil-free scroll type air compressors having the tip seal and fixed-radius orbiting mechanisms was investigated theoretically and experimentally. The volumetric and total efficiencies of the compressor were reasonable, about 87 % and 56 % respectively under the condition of discharge pressure 700 kPa(gauge) and rotational speed 2720 rpm. The most dominant factor lowering the total compressor efficiency was the leakage through the radial clearance between the scroll wraps. The compressor performance was little dependent on the change of discharge pressure, but it changed favorably with the increase of rotational speed. The mixing of water into the suction air was very effective for the improvement of compressor performance, and then the volumetric efficiency was close to 100 % and the total compressor efficiency was over 70 %.