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Transient Lift-Off Test Results for an Experimental Hybrid Bearing in Air, Simulating a Liquid Hydrogen Turbopump Start Transient

[+] Author Affiliations
Dara W. Childs, Stephen Phillips

Texas A&M University, College Station, TX

David Klooster

Luminant, Glen Rose, TX

Henry Borchard

Chevron ETC, Houston, TX

Dustin Pavelek

Kelm Engineering, LLC, Friendswood, TX

Paper No. GT2016-56310, pp. V07BT31A009; 13 pages
  • ASME Turbo Expo 2016: Turbomachinery Technical Conference and Exposition
  • Volume 7B: Structures and Dynamics
  • Seoul, South Korea, June 13–17, 2016
  • Conference Sponsors: International Gas Turbine Institute
  • ISBN: 978-0-7918-4984-2
  • Copyright © 2016 by ASME


Start-transient testing of a hybrid (combined hydrostatic and hydrodynamic action) bearing supplied with air was completed, providing an indication of its performance while operating in a compressible fluid medium. The test start transients were modeled after Rocket Engine Transient Simulation Software (ROCETS) predictions for start-transient behavior of running speed ω(t) and bearing supply pressure Ps(t). The top test speed was 15 krpm. The ramp rate, supply pressure Ps values at 15 krpm, constant bearing unit load magnitude w0, and load orientation (load-on-recess LOR or load-on-land LOL) were varied. Five different load-case combinations were carried out (separately) for LOR and LOL load configurations with ramp rates varying from 2206 rpm/s to 8824 rpm/s. The target pressures at 15 krpm varied from 5.32 bars to 18.25 bars.

The tested bearing dimensions were: L = D = 38.1 mm, and Cr =.0635 mm. Lift-off occurs due to the increase in Ps (ω dependent) and was defined as the point of departure towards the center of the bearing with increasing ω while the rotor remained 0.00254 mm (0.1 mils) above the bearing surface. This method is limited by the inability to accurately measure an established operating bearing clearance.

Evaluation of the lift-off Ps versus applied unit load w0 supports the following conclusions: (1) Lift-off Ps is approximately a linear function of w0, (2) Changing the ramp rate while keeping constant the specified Ps at 15 krpm has no significant impact, (3) Lowering the limit Ps at 15 krpm may reduce the lift-off Ps value, and (4) The LOR start-transient cases required a higher lift-off speed and lift-off Ps values than the corresponding LOL start-transient cases.

Copyright © 2016 by ASME



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