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Title: Mathematical modelling of air-rotor-stator interactions in high-speed air-riding bearing and seal technology /
Author: Garratt, John Edward
ISNI:       0000 0004 2746 6230
Awarding Body: University of Nottingham
Current Institution: University of Nottingham
Date of Award: 2010
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Air-riding bearing and seal technology comprises rotor and stator elements separated by a thin air-film and experiencing relative rotational motion. The Navier- Stokes equations for compressible flow lead to a modified Reynolds equation incorporating additional high-speed rotation effects. The dynamics of the system are investigated when the axial position of the stator is prescribed by a finite amplitude periodic forcing. Two different physical configurations of air-riding technology are considered in this thesis; a squeeze-film thrust bearing and a pressurised air-riding face seal. Details are provided of a finite-difference, time-stepping scheme and a Fourier spectral collocation scheme to compute the periodic pressure distributions and rotor heights. For changing values of a selected physical parameter the method of arc-length continuation is employed to track branches of solutions computed using the spectral collocation scheme. For both configurations of air-riding technology the effect of different frequencies and amplitudes of stator forcing is identified for a range of rotation speeds and the influence of the rotor support structures is analysed. For air-riding face seals a critical shaft speed is identified that maintains no-net flow by balancing inertia and pressurisation effects The potential for resonant rotor behaviour is identified through asymptotic and Fourier analysis of the rotor motion. Changes in the minimum rotor-stator clearance are presented as a function of the rotor stiffness to demonstrate the appearance of resonance. Both the minimum rotor-stator clearance and the total mass flux of air through the seal are used to evaluate the limits of stable periodic operation without resonant rotor dynamics and incorporating high operating speeds.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available