Experimental investigation of geometry-induced sealing–load trade-off in twin-screw pump rotor profiles

Rotor profile geometry fundamentally governs the internal sealing, leakage characteristics, and mechanical loading behavior of twin-screw pumps. Classical Quimby profiles are widely adopted for their conjugate involute–epicycloid construction and improved volumetric sealing, whereas multiphase rotor designs modify contact topology to redistribute mechanical loading. However, quantitative experimental evidence demonstrating the trade-off between volumetric efficiency and shaft loading remains limited. This work presents an analytical and experimental comparison of Quimby and multiphase rotor profiles under identical outer diameter, lead, rotor length, and clearance values to isolate pure geometric profile effects. Mathematical formulations are developed to evaluate cross-sectional fluid area and theoretical flow rate, followed by the proposed leakage model, which is validated through experimental estimation of the leakage coefficient, demonstrating consistency with the assumed linear relationship between leakage flow and pressure difference over a pressure range of 4–14 bar using ISO VG 46 oil. Experimental results indicate that the Quimby rotor achieves approximately 1.5–2% higher volumetric efficiency, while the multiphase rotor reduces torque and power consumption by approximately 1–2% under identical operating conditions. The findings demonstrate an intrinsic geometry-driven trade-off between sealing performance and mechanical loading. A Mechanical Load Index is introduced to quantify this balance and provide a geometry-based selection framework for application-specific twin-screw pump design.