The contact line of a twin-screw air compressor is the spatial curve formed by the tooth surfaces of the two rotors contacting each other when the male and female rotors of the compressor mesh. In actual air compressors, due to the existence of inter-tooth gaps, the theoretical contact line evolves into a practical gap zone. Since the points on the contact line on the male and female screw tooth surfaces are in meshing state at this moment, the screw tooth surfaces The gap between the teeth is minimal along the upper contact line. The most critical component in a screw compressor is a pair of intermeshing screw rotors. The intersection line between the rotor tooth surface and the vertical plane of the rotor axis is called the screw rotor profile. Since the spiral movement of the rotor profile forms the tooth surface of the rotor, the rotor profile is also called the end profile or rotor tooth profile. The profile design of the yin and yang rotors of the screw compressor satisfies the yoke meshing law, that is, the common normal passing through the profile contact point must pass through the node at any position. In fact, the tooth surface of the screw air compressor is mainly used to compress gas. It uses the grooves and convex teeth of the Yin and Yang screws to mesh with each other to form a cavity. Its Yin and Yang rotors do not contact each other, and the power transmission between the two This is done through synchronized gears. In addition to meeting the yoke conditions and being easy to process, the screw rotor tooth shape must also have good axial and transverse air tightness, a large volume, and a large exhaust port. Therefore, the rotor profile of a screw air compressor is usually composed of multiple curves such as points, straight lines, cycloids, arcs, ellipses and parabolas connected end to end; the most important thing in the design of a screw air compressor is the design of the rotor profile. The rotor profile basically determines the quality of the screw air pressure performance.