Single screw star wheel suction process. The screw groove is connected to the suction chamber before the planetary gear teeth are engaged, and is in a suction state. When the screw rotates to a certain position, the star gear teeth seal the screw groove, and the suction process ends (Figure a). 2) Compression process. After the inhalation process is completed, the screw continues to rotate, and as the planetary gear teeth advance along the screw groove, the enclosed interdental volume gradually decreases, achieving the compression process of gas. When the interdental volume is connected to the exhaust port, the compression process ends (Figure b). 3) Exhaust process. After the inter tooth volume is connected to the exhaust port, due to the continued rotation of the screw, the compressed gas is transported through the exhaust port to the exhaust pipe until the planetary gear teeth detach from the screw groove (Figure c). From the above working principle, it can be seen that a single screw air compressor has an internal compression process. The gas is first sucked in and then enclosed in the interdental volume between the screw, casing, and star wheel, and the compression of the gas is achieved by the reduction of the interdental volume. The degree of internal compression is determined by the position of the designed exhaust port. The content volume ratio of a single screw air compressor generally ranges from 2 to 5.