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TECHNICAL PAPERS: Gas Turbines: Structures and Dynamics

Operation of a Mesoscopic Gas Turbine Simulator at Speeds in Excess of 700,000rpm on Foil Bearings

[+] Author and Article Information
Mohsen Salehi

 Mohawk Innovative Technology, Inc., Albany, NY 12205salehim@asme.org

Hooshang Heshmat, James F. Walton, Michael Tomaszewski

 Mohawk Innovative Technology, Inc., Albany, NY 12205

J. Eng. Gas Turbines Power 129(1), 170-176 (Mar 01, 2004) (7 pages) doi:10.1115/1.2360600 History: Received October 01, 2003; Revised March 01, 2004

A small mesoscopic gas turbine engine (MGTE) simulator was tested at speeds over 700,000rpm. The MGTE was operated with specially designed miniature compliant foil journal and thrust air bearings. The operation of the simulator rotor and foil bearing system is a precursor to development of turbine powered micro-aerial vehicles and mesoscopic power generators. The foil bearings use a new fabrication technology in which each bearing is split. This feature permits the use of these bearings in highly advanced engines where single piece ceramic rotors may be required. The simulator weighed 56g (including the 9g rotor) and included two non-aerodynamic wheels to simulate the compressor and turbine wheels. Each compliant foil journal bearing had a diameter of 6mm and was located equidistant from each end of the rotor. Experimental work included operation of the simulator at speeds above 700,000rpm and at several different orientations including having the spin axis vertical. Results of the rotor bearing system dynamics are presented along with experimentally measured natural frequencies at many operating speeds. Good correlation between measurement and analysis is observed indicating the scalability of the analysis tools and hardware used. The rotor was very stable and well controlled throughout all testing conducted. Based on this successful testing it is expected that the goal of operating the rotor at speeds exceeding 1 million rpm will be achieved.

Copyright © 2007 by American Society of Mechanical Engineers
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Figures

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Figure 1

Microturbine cycle analysis results

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Figure 2

Comparison of foil and ball bearing power loss versus speed

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Figure 3

Assembled and instrumented mesoscopic simulator

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Figure 4

Schematic of the nozzle box

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Figure 5

The rotor hardware with mesoscale turbine

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Figure 6

Schematic of the split bearing shell

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Figure 7

Cross section of dynamic simulator

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Figure 8

Stiffness coefficients as a function of speed

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Figure 9

Whirl speed map showing mode shapes and both predicted and measured natural frequencies as a function of spin speed

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Figure 10

Stability map—logarithmic decrement versus rotor speed for the two rigid body natural frequencies

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Figure 11

Rotor frequency spectrum for horizontal position at 675,000rpm

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Figure 12

Spectrum for 90deg roll about spin axis

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Figure 13

Spectrum for 180deg roll about spin axis

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Figure 14

Spectrum for vertical operation

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Figure 15

Waterfall frequency spectrum showing operation above 700,000rpm, from startup to shutdown

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