The Role of Recess Configuration and Working Fluid in Hybrid Bearing Performance

Abstract Hybrid bearings, combining hydrostatic and hydrodynamic lubrication principles, are essential for supporting modern highspeed, high-power cryogenic rocket engine turbopumps. These bearings provide the necessary stiffness and load-carrying capacity for stable operation across a wide range of speeds. This study investigates design strategies for hybrid bearings lubricated with various fluids, including air, helium, liquid methane (LCH4), liquid oxygen (LOX), liquid nitrogen (LN2), and water. Each fluid presents unique challenges related to pressure, flow, and operating conditions, necessitating precise modifications in bearing geometry. A comprehensive analysis is conducted to assess the influence of key design parameters on both static and dynamic bearing performance. These parameters include the recess depth, recess area, recess aspect ratio, number of recesses, and arrangement of recesses. The impact of these factors on bearing stiffness and load capacity is evaluated across a range of operating conditions, including bearing unit load, rotor speed, eccentricity, and fluid supply pressure. Dimensionless parameters, such as the ratio of bearing area to recess area, bearing length to recess length, and bearing clearance to journal radius, are employed to characterize bearing behavior. This research provides valuable insights and practical guidelines for selecting hybrid bearing geometry for diverse fluids and operating conditions. By elucidating the complex interplay between fluid properties and bearing configurations, this study contributes to the advancement of high-speed rotating machinery design, particularly for demanding cryogenic applications.