| Summary: | 碩士 === 國立屏東科技大學 === 機械工程系所 === 101 === Critical core elements within a twin-screw compressor include a pair of mutually meshing screw rotors, whereas key factors of leakage paths and geometric characteristics that affect the performance of compressors include rotor tooth surface contact lines, leakage blowhole, trapped volumes, and tooth groove volumes. In this work, we will establish a mathematical model of rotor profile generation using the sealing line of the rotors, use quadratic equations to control the shapes of the various sealing sections, as well as apply constraints. Tooth profile for a pair of conjugate twin-screw rotors are derived according to coordinate transformtion and envelope theory. In addition, this work looks into the changes in clearance on the contact line with respect to the rotation angle of the male rotor during meshing operation, finds the contact zone on the contact line and establishes the polar expression. The radius of the contact zone control points and the pressure angles are used as design parameters for defining the contact zone curve equation. Furthermore, the effects of the geometric shape of the contact area on compressor performance indices are studied. The performance indices discussed in this work include compressor efficiencies, specific sliding, tooth diffrential contact force, and gas internal torque. The higher specific sliding and tooth diffrential contact force, the greater the wear on the tooth surfaces; the larger the variation in torque, the less stable the operation of the rotor (which could also be accompanied by relatively larger vibrations and noise). Therefore, this study looks into the trends of performance indices using contact zone line control parameters as design variables, thereby obtaining the effects of change in the geometric shape of contact zone on performance indices to serve as a reference for tooth design concerning sealing lines as well as a theoretic basis for the improvement of twin-screw compressor performance.
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