Geometric and Numerical Investigation of Twin-Screw Vacuum Pumps

This paper presents analysis of twin-screw vacuum pumps, encompassing both geometrical calculations and numerical simulations. The geometrical calculations include key parameters such as chamber volume, leakage area, suction port area, and discharge port area. These parameters are studied across rotational angles for constant pitch, and stepped pitch configurations. The leakage areas include radial, axial, and interlobe leakage paths. Computational Fluid Dynamics (CFD) is employed to investigate the axial leakage paths. Additionally, the study utilizes the SCORG software package, an inhouse simulation tool to calculate thermodynamic processes and integral parameters. By integrating the geometric calculations into SCORG, this approach enables extensive calculation and design optimization of twin-screw vacuum pumps. Five different combinations of pitch were analyzed to assess their impact on both volume flow rate and efficiency. The analysis revealed that reducing the pitch of the second stage resulted in a decrease of approximately 2% in volumetric efficiency, while adiabatic efficiency increased by around 4%. The findings contribute to a more comprehensive understanding of the performance characteristics and design considerations for twin screw vacuum pump.