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TECHNICAL PAPERS: Gas Turbines: Structures and Dynamics

Nonlinear Rotordynamics of Automotive Turbochargers: Predictions and Comparisons to Test Data

[+] Author and Article Information
Luis San Andrés

Mechanical Engineering Department, Texas A&M University, College Station, TX 77843lsanandres@mengr.tamu.edu

Juan Carlos Rivadeneira

Mechanical Engineering Department, Texas A&M University, College Station, TX 77843

Murali Chinta

 Honeywell Turbo Technologies, Torrance, CA 90505

Kostandin Gjika

 Honeywell Turbo Technologies, 88155 Thaon les Vosges, France

Gerry LaRue

 Honeywell Turbo Technologies, Torrance, CA 90905

J. Eng. Gas Turbines Power 129(2), 488-493 (Sep 28, 2005) (6 pages) doi:10.1115/1.2204630 History: Received August 25, 2005; Revised September 28, 2005

Passenger vehicle turbochargers (TCs) offer increased engine power and efficiency in an ever-competitive marketplace. Turbochargers operate at high rotational speeds and use engine oil to lubricate fluid-film-bearing supports (radial and axial). However, TCs are prone to large amplitudes of subsynchronous shaft motion over wide ranges of their operating speed. Linear rotordynamic tools cannot predict the amplitudes and multiple frequency shaft motions. A comprehensive nonlinear rotordynamics model coupled to a complete fluid-film-bearing model solves in real time the dynamics of automotive turbochargers. The computational design tool predicts the limit cycle response for several inner and outer film clearances and operating conditions including rotor speed and lubricant feed pressure. Substantial savings in product development and prototype testing are the benefits of the present development. The paper presents predictions of the linear and nonlinear shaft motion of an automotive turbocharger supported on a semi-floating ring bearing. The shaft motion predictions are compared to measurements of shaft motion at the compressor nose for speeds up to 240krpm, and for lubricant inlet pressure of 4bar at 150°C. Linear and nonlinear rotordynamic models reproduce very well the test data for synchronous response to imbalance. The nonlinear results show two subsynchronous whirl frequencies whose large magnitudes agree well with the measurements. A large side load predicted for this turbocharger must be considered for accurate prediction of the rotordynamic response.

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Copyright © 2007 by American Society of Mechanical Engineers
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Figures

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Figure 1

Photograph of automotive turbocharger supported on semi-floating ring bearings

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Figure 2

Waterfall of turbocharger measured shaft displacement versus frequency. Shaft speed ranges from 29.7krpm to 243.8krpm. 4bar(150°C) oil feed pressure. Vertical eddy current sensor (compressor side).

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Figure 3

Structural FE model of turbocharger rotor and semi-floating ring bearing. Location of mass imbalance planes noted.

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Figure 4

Free-free mode shapes for turbocharger rotor—predictions and measurements at room temperature

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Figure 5

Predicted damped natural frequencies versus shaft speed for test turbo charger rotor. Damped natural modes shown for shaft speed=100krpm.

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Figure 6

Waterfall of predicted nonlinear (vertical) shaft motions at compressor end. Rotor range speed 29.7 to 244krpm. 4bar lubricant feed pressure. Amplitude refractive to maximum physical limit.

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Figure 7

FFTs of shaft motion at compressor end for rotor speeds equal to 127krpm (bottom) and 205krpm (top). Comparison of nonlinear predictions to test data. Note amplitudes at subsynchronous frequencies.

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Figure 8

Amplitudes of total motion at compressor end versus shaft speed. Comparisons between test data and nonlinear predictions. Oil feed pressure=4bar(150°C).

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Figure 9

Amplitudes of synchronous shaft motion versus shaft speed. Comparisons between test data and linear and nonlinear predictions. Oil feed pressure=4bar(150°C).

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Figure 10

(a) Whirl frequency of subsynchronous motions and (b) whirl frequency ratios versus shaft speed. Comparisons between nonlinear predictions and test data. Lines represent damped natural frequencies (linear analysis). Oil feed pressure=4bar(150°C).

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Figure 11

Amplitudes of subsynchronous motions versus (a) shaft speed and (b) whirl frequency. Comparisons between nonlinear predictions and test data. Oil feed pressure=4bar.

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