Research Papers: Gas Turbines: Structures and Dynamics

Synchronous Response to Rotor Imbalance Using a Damped Gas Bearing

[+] Author and Article Information
Bugra H. Ertas

Rotating Equipment Group, Vibration and Dynamics Laboratory, GE Global Research Center, Niskayuna, NY 12309ertas@research.ge.com

Massimo Camatti

Conceptual Design, Advanced Technology, GE Oil and Gas, Florence, Italy FI-50127massimo.camatti@ge.com

Gabriele Mariotti

Mechanical Design, Turboexpander Division, GE Oil and Gas, Florence, Italy FI-50127gabriele.mariotti@ge.com

J. Eng. Gas Turbines Power 132(3), 032501 (Dec 01, 2009) (9 pages) doi:10.1115/1.3157097 History: Received March 19, 2009; Revised March 22, 2009; Published December 01, 2009; Online December 01, 2009

One type of test performed for evaluating bearings for application into turbomachinery is the synchronous bearing response to rotor imbalance. This paper presents rotordynamic tests on a rotor system using a 70 mm diameter damped gas bearing reaching ultra-high speeds of 50,000 rpm. The main objective of the study was to experimentally evaluate the ability of the damped gas bearing to withstand large rotor excursions and provide adequate damping through critical speed transitions. Two critical speeds were excited through varying amounts and configurations of rotor imbalance while measuring the synchronous rotordynamic response at two different axial locations. The results indicated a well-damped rotor system and demonstrated the ability of the gas bearing to safely withstand rotor vibration levels while subjected to severe imbalance loading. Also, a waterfall plot was used to verify ultra-high-speed stability of the rotor system throughout the speed range of the test vehicle. In addition to the experimental tests, a rotordynamic computer model was developed for the rotor-bearing system. Using the amplitude/frequency dependent stiffness and damping coefficients for the ball bearing support and the damped gas-bearing support, a pseudononlinear rotordynamic response to imbalance was performed and compared with the experiments.

Copyright © 2010 by American Society of Mechanical Engineers
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Figure 1

Test rig layout and cross section

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Figure 2

Rotor support configurations

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Figure 3

Compliant hybrid gas bearing using integral wire mesh bearing support dampers (6)

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Figure 4

Machine imbalance grades, rotor modes, and experimental test matrix

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Figure 5

Baseline test with 0.20 g in. rotor imbalance: 8.1×10−06 lb in./lb specific residual imbalance

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Figure 7

SFD and squirrel cage design parameters

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Figure 8

WMD and integral spring design parameters

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Figure 9

SFD and WMD nonlinear stiffness coefficients

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Figure 10

SFD and WMD nonlinear damping coefficients

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Figure 11

Iteration scheme using nonlinear coefficients

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Figure 12

Experimental results versus rotordynamic simulations



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