Squeeze Film Forces in a Magnetic Shaft Suspension System

Abstract

Viscous squeeze film forces were studied as they pertain to a magnetic shaft suspension system (magnetic bearing). A nonrotating magnetically suspended shaft generates hydrodynamic fluid forces as it oscillates radially within a close fitting concentric cylinder. Experimental results from a scaled model verify the theoretical analysis. The study includes the finite and infinite length cases (1/4<L/D<8) for large diameter to clearance ratios (D/c>50). The viscous squeeze film forces increase the phase margin in the magnetic bearing closed-loop control systems used in state-of-the-art cryogenic refrigerators.