Single-screw pump is a positive displacement pump, which relies on screw and bushing intermeshing in the suction chamber and the discharge chamber to produce volume changes to transport liquid. It is an internal mesh enclosed screw pump. The main working part consists of a bushing (stator) with a double-headed helical cavity and a single-headed helical screw (rotor) engaged with it in the stator cavity. When the input shaft drives the rotor through the universal joint to revolve around the center of the stator, the stator-rotor pair continuously mesh with each other to form a sealed chamber. The volume of the sealed chamber is uniformly and axially moved at constant speed, and the medium is transported from the suction end through the stator - The rotor is fed to the press-out end and the medium drawn into the closed chamber flows through the stator without being agitated and destroyed. Screw has a single thread, any section of which are R radius of the circle, the center of the cross section is located on the helix and the axis of the screw deviation from an eccentricity e, around the axis of rotation and the axial movement of the liner The inner surface has a double thread, an arbitrary section of which is an ellipse, the two ends are semicircles with a radius R (equal to the radius of the screw section), and the middle section is a straight section with a length of 4e. Any section of the bushing is the same oval, just offset from each other by an angle. After the screw is inserted into the bushing, the closed cavity is formed between the screw surface and the internal thread surface of the bushing, and the arbitrary cross section is also divided into two upper and lower crescent-shaped working chambers (as shown in FIG. 1-3). As the screw rotates, the volume of the first working chamber near the suction chamber gradually increases to create a negative pressure, and the liquid is drawn into the working chamber by the pressure difference. As the screw continues to rotate, the working chamber volume increases to the maximum, the working chamber is closed, and the liquid is pushed axially toward the pressure chamber. At the same time, the upper and lower chambers alternately suck and discharge the liquid cyclically, so that the liquid is continuously and axially pushed from the suction chamber toward the pressure chamber.