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TECHNICAL PAPERS

Rotordynamics of Small Turbochargers Supported on Floating Ring Bearings—Highlights in Bearing Analysis and Experimental Validation

[+] Author and Article Information
Luis San Andres, Juan Carlos Rivadeneira

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

Kostandin Gjika, Christopher Groves

 Honeywell Turbo Technologies, 88155 Thaon les Vosges, France

Gerry LaRue

 Honeywell Turbo Technologies, Torrance, CA 90505

J. Tribol 129(2), 391-397 (Nov 13, 2006) (7 pages) doi:10.1115/1.2464134 History: Received February 18, 2006; Revised November 13, 2006

Turbochargers (TCs) improve performance in internal combustion engines. Due to low production costs, TC assemblies are supported on floating ring bearings (FRBs). TCs show subsynchronous motions of significant amplitudes over a wide speed range. However, the subsynchronous whirl motions generally reach a limit cycle enabling continuous operation. The paper advances progress on the validation against measurements of linear and nonlinear rotordynamic models for predicting shaft motions of automotive TCs. A comprehensive thermohydrodynamic model predicts the floating ring speeds, inner and outer film temperatures and lubricant viscosity changes, clearances thermal growth, operating eccentricities for the floating ring and journal, and linearized force coefficients. A nonlinear rotordynamics program integrates the FRB lubrication model for prediction of system time responses under actual operating conditions. Measurements of shaft motion in a TC unit driven by pressurized air demonstrate typical oil-whirl induced instabilities and, due to poor lubricant conditions, locking of the floating rings at high shaft speeds. Nonlinear predictions are in good agreement with the measured total amplitude and subsynchronous frequencies when implementing the measured ring speeds into the computational model. The computational tools aid to accelerate TC prototype development and product troubleshooting.

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Copyright © 2007 by American Society of Mechanical Engineers
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Figures

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Figure 1

Schematic view of floating ring bearing thermal flow model

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Figure 2

Photograph of test turbocharger supported on floating ring bearings

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Figure 3

Waterfall of measured shaft motions at compressor end of TC rotor. 38°C lubricant inlet temperature and 206kPa supply pressure.

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Figure 4

Amplitude of measured synchronous and subsynchronous motions at compressor end versus shaft speed. 38°C lubricant inlet temperature and 206kPa supply pressure.

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Figure 5

Predicted and measured floating ring speed ratios for (a) compressor and (b) turbine bearings. Lubricant inlet temperature 38°C, 206kPa feed pressure.

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Figure 6

Predicted and measured lubricant exit temperature. 38°C lubricant inlet temperature 206kPa supply pressure.

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Figure 7

Turbocharger rotordynamic model. Location of imbalance planes and recorded shaft motions noted.

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Figure 8

Waterfall of predicted vertical shaft motions at the compressor end of TC rotor. 38°C lubricant inlet temperature and 206kPa supply pressure. Floating ring speeds taken from predictions.

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Figure 9

Waterfall of predicted vertical shaft motions at the compressor end of TC rotor. 38°C lubricant inlet temperature and 206kPa supply pressure. Floating rings locked (no rotation) at shaft speeds >50krpm.

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Figure 10

Waterfall of predicted vertical shaft motions at the compressor end of TC rotor. 38°C lubricant inlet temperature and 206kPa supply pressure. Floating ring speeds taken from test data.

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Figure 11

Total motion versus shaft speed at compressor end of TC rotor. 38°C lubricant inlet temperature and 206kPa supply pressure. Floating ring speeds taken from test data.

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Figure 12

Amplitudes of subsynchronous motions versus shaft speed at compressor end of TC rotor. 38°C lubricant inlet temperature and 206kPa supply pressure. Floating ring speeds taken from test data.

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Figure 13

Whirl frequency of subsynchronous motions versus shaft speed at compressor end. 38°C lubricant inlet temperature and 206kPa supply pressure. Floating ring speeds taken from test data.

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