Numerical modeling and design decisions for aerostatic bearings with relatively large nozzle sizes in Magic-Angle Spinning (MAS) systems

Numerical stability analysis for aerostatic bearings was performed to obtain optimized design parameters small submillimeter millimeter range diameter cylindrical rotors. Such rotors are used in nuclear magnetic resonance (NMR) application rotate sample around an axis inclined by magic angle (54.74o) relative the field direction at rotational frequencies of about 100 kHz (magic-angle spinning, MAS). The governing Reynolds equation fluid film between rotor and bearing modified size with relatively large nozzle diameters. solved using a finite-volume method pressure thickness rotor. This led solution maximum stable inertial force as function frequency parameters. comparison infinitesimal sizes obtained supported weight critical vibrational found correspond specific rotor–bearing clearance. investigation also shows enhancement decreasing number or increasing molecular mass impinging gas Experimental observations further confirmed role diameter, enhancing spinning frequency. Further, decisions were made based on such tested varying properties. Using optimization numerical simulation, rotation home-built 0.4mm MAS could be enhanced from 25 up 110 kHz, still below extrapolation