Vibration isolation Performance of Disk-Type Permanent Magnetic Thrust Bearings in Propulsion Shaft Systems: A Comprehensive Study of Theories and Experiments

Propulsion shaft systems using permanent magnetic thrust bearings (PMTBs) leverage non-contact magnetic interactions to enhance thrust transmission and provide superior longitudinal vibration isolation compared to traditional tilt-pad bearings. Cylinder-type PMTBs are commonly employed; however, their magnetic stiffness diminishes under high static loads, rendering them particularly suitable for heavy-load conditions. However, most propulsion systems operate under lower loads, requiring improved vibration isolation in light-load conditions. Disk-type PMTBs offer an effective solution, excelling in vibration isolation at light loads while maintaining load-bearing capacity. Since PMTBs are not yet widely used, research on disk-type PMTBs remains limited. This study investigates the load-bearing and vibration isolation performance of disk-type PMTBs, designing a bidirectional load-bearing configuration and exploring its mechanisms using the equivalent magnetic charge method. The results show that disk-type PMTBs have significantly lower magnetic stiffness than cylinder-type PMTBs under light loads, indicating better longitudinal vibration isolation. A dynamic model is developed using the harmonic balance method, with force transmissibility as the metric. Nonlinear dynamic responses of disk-type PMTBs under varying static and dynamic loads exhibit both hardening and softening behaviors. Experimental validation through harmonic excitation and white noise signals confirms the superior vibration isolation performance of disk-type PMTBs in light-load conditions.