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TECHNICAL PAPERS

Thermal Assessment of Dynamic Rotor/Auxiliary Bearing Contact Events

[+] Author and Article Information
Patrick S. Keogh1

Department of Mechanical Engineering, University of Bath, Bath BA2 7AY, UKenspsk@bath.ac.uk

Woon Yik Yong

Department of Mechanical Engineering, University of Bath, Bath BA2 7AY, UK

1

Corresponding author.

J. Tribol 129(1), 143-152 (Jun 27, 2006) (10 pages) doi:10.1115/1.2401209 History: Received March 17, 2006; Revised June 27, 2006

Under normal operation, a rotor levitated by magnetic bearings will rotate without making contact with any stator component. However, there are a number of circumstances that may lead to temporary or permanent loss of levitation. These include full rotor drop events arising from power loss, momentary fault conditions, sudden changes in unbalance, high levels of base acceleration, and other aerodynamically induced force inputs. The spinning rotor will come into dynamic contact with an auxiliary bearing. Highly localized and transient temperatures will arise from frictional heating over the dynamically varying contact area. Rotor dynamic contact forces are predicted for a range of initial conditions leading to combinations of bounce and rub motion on the auxiliary bearing. The transient heat flux from the contact area is then ascertained. A transient thermal Green’s function is developed in a form that is effective over short or long time scales and local to the source. This enables the transient thermal response of an auxiliary bearing to be assessed for a range of dynamic contact conditions. Auxiliary bearings consisting of fixed bushings and free to rotate inner races are analyzed. The results show that significant localized contact temperatures may arise from each contact event, which would accumulate for multiple contact cases. The methodology will be of relevance for the life prediction of auxiliary bearing designs.

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Copyright © 2007 by American Society of Mechanical Engineers
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Figures

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Figure 4

Contact dynamic response with Ω=1000rad∕s, V=0.1m∕s, β=−90deg, kb=2×107N∕m, cb=4×104Ns∕m, μ=0.1

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Figure 5

Time dependence of Green’s function spatial harmonic coefficients showing smooth behavior over short timescales

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Figure 6

Time variation of fixed bushing auxiliary bearing inner surface temperature for different levels of contact force

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Figure 7

Time variation of fixed bushing auxiliary bearing inner surface temperature for different contact periods

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Figure 8

Angular variation of fixed bushing auxiliary bearing inner surface temperature at selected times. The contact period was tp=1ms.

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Figure 9

Angular variation of fixed bushing auxiliary bearing inner surface temperature at selected times. The contact period was tp=1ms.

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Figure 10

Contour plots of localized auxiliary bearing temperature rise (K) after: (a)1ms; (b)10ms; and (c)200ms. The data of Fig. 8 apply.

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Figure 11

Inner race angular speed for a single rotor bounce with different coefficients of friction

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Figure 12

Time variation of inner race of auxiliary bearing inner surface temperature for different coefficients of friction. θp corresponds to the angle at which the temperature is a maximum.

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Figure 13

Time variation of inner race of auxiliary bearing inner surface temperature for different dynamic contact conditions

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Figure 14

Angular variation of inner race auxiliary bearing inner surface temperature at selected times. Data as for the higher case of Fig. 1.

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Figure 1

Rotor/magnetic/auxiliary bearing model. The common origin O, displaced for the Cartesian coordinates shown, is the geometric center of the magnetic bearing.

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Figure 2

Contact dynamic response with Ω=1000rad∕s, V=0.1m∕s, β=135deg, kb=2×108N∕m, cb=1×104Ns∕m, μ=0.1

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Figure 3

Contact dynamic response with Ω=1000rad∕s, V=0.2m∕s, β=135deg, kb=4×108N∕m, cb=1×104Ns∕m, μ=0.1

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