Hybrid Fluid Film Bearing Supported Electric Pumps for Liquid Rocket Engines: Rotor-Bearing System Design and Rotordynamic Simulator Testing

Abstract This study investigates the feasibility of employing electric motor-driven pumps supported on hybrid fluid film bearings for propellant supply in liquid rocket engines. This approach, particularly suited for reusable small- to medium-sized launch vehicles, leverages recent advancements in battery energy density to offer a potential alternative to traditional turbopumps. The electric pump design utilizes the inducer and impeller from the oxidizer pump of an existing Korean Space Launch Vehicle turbopump, replacing the turbine with a high-power electric motor. The structural design prioritizes weight reduction while accommodating centrifugal forces and thermal expansion of the pump rotating shaft. A comprehensive rotordynamic analysis, incorporating rotor, bearing, seal, and housing stiffness, is performed. This analysis considers various models and evaluates the static and dynamic characteristics of the hybrid fluid film bearings under a range of operating conditions. To validate the final rotor-bearing model, a dedicated rotordynamic simulator is designed and fabricated. This simulator incorporates a flexible coupling to an electric motor and enables testing with liquid nitrogen. Experimental measurements of rotor dynamic motion and vibration across various rotor speeds and fluid pressure conditions demonstrate good agreement with model predictions, confirming the accuracy of the bearing performance predictions. This research provides a foundational study for the development of electric pump systems utilizing hybrid fluid film bearings, paving the way for their potential application in future reusable rocket engines.