Abstract: Abstract： A 3D geometry model of a twin screw expander was developed using PROE to measure and analyze geometric parameters such as groove volume, suction port area and leakage area as a function of rotation angle of the male rotor. Then, based on the geometry model, a thermodynamic model was developed using the continuity and energy conservation equation and taking the suction loss, leakage loss and real gas effect into consideration. Based on the model, the mass flow rate through inlet port and leakage path as a function of rotation angle of male rotor as well as the effects of expander inlet parameter and operating parameter on the performance of the expander was analyzed. It is found that leakage in the suction process and the early stage of expansion process is one of the main factors affecting the internal efficiency, leakage through contact line and rotor tiphousing clearance is the main leakage path, and that the increase in inlet pressure and decrease in rotor speed would lead to the increase of leakage mass.

Key words: Key words： screw expander, 3D model, simulink, leakage, internal efficiency