Effect of Radial Clearance on Static and Dynamic Performances of Single-Structured Hybrid Gas-Magnetic Bearing Rotor System

As the demand for ultrahigh-speed bearings grows, hybrid gas-magnetic bearings (HGMBs) have emerged as a research focus due to the ability to integrate the merits of active magnetic bearings (AMBs) and gas bearings (GBs). However, HGMBs face challenges related to complex structure and manufacturing. This study emphasizes the critical role of radial clearance in HGMB design, as excessive clearance reduces GB load capacity and stability. In contrast, insufficient clearance increases the risk of rotor–stator contact and is prone to thermal runaway failure or bearing seizure. This work investigates the comprehensive performance of HGMBs with varying clearances. The results show that radial clearance significantly influences GB and HGMB load capacities, with a 30-μm clearance increasing GB capacity up to 16.8 times compared to 150 μm at 46 krpm. Increasing radial clearance also reduces total losses in AMB, GB, and HGMB, notably decreasing GB air friction loss by up to 80.1%. The AMB/HGMB total loss increases tremendously with rotor eccentricity, especially in larger radial clearances. In addition, higher clearances lead to increased instability and vibration, with GB being the most sensitive. HGMBs exhibit superior startup stability, while zero-bias HGMBs and AMBs face challenges with increasing radial clearance. These findings highlight the importance of considering radial clearance effects and provide valuable insights for HGMB design, promoting advancements in this technology and engineering applications.