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TECHNICAL PAPERS: Gas Turbines: Structures and Dynamics

A Virtual Tool for Prediction of Turbocharger Nonlinear Dynamic Response: Validation Against 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

Kostandin Gjika, Christopher Groves

 Honeywell Turbo Technologies, 88155 Thaon les, Vosges, France

Gerry LaRue

 Honeywell Turbo Technologies, Torrance, CA 90505

J. Eng. Gas Turbines Power 129(4), 1035-1046 (Jul 20, 2006) (12 pages) doi:10.1115/1.2436573 History: Received July 19, 2006; Revised July 20, 2006

Advances on the modeling of nonlinear rotor-bearing models for prediction of the dynamic shaft response of automotive turbochargers (TCs) supported on floating ring bearings (FRBs) are presented. Comprehensive test data for a TC unit operating at a top speed of 65krpm serves to validate the model predictions. The static forced performance of the support FRBs considers lubricant thermal effects, thermal expansion of the shaft and bearings, and entrance pressure losses due to centrifugal flow effects. The bearing analysis also yields linearized rotordynamic force coefficients for the inner and outer lubricant films. These coefficients are used with the rotor model to predict the synchronous response to imbalance and the system natural frequencies and stability. A method renders an accurate estimation of the test rotor imbalance by using the actual vibration measurements and influence coefficients derived from predictions using linearized bearing force coefficients. Predicted ring rotational speeds, operating radial clearances, and lubricant viscosities for the inner and outer films are the main input to the nonlinear time transient analysis. The nonlinear response model predicts the total shaft motion, with fast Fourier transforms showing the synchronous response, and amplitudes and whirl frequencies of subsynchronous motions. The predicted synchronous amplitudes are in good agreement with the measurements, in particular at high shaft speeds. The nonlinear analysis predicts multiple frequency subsynchronous motions for speeds ranging from 10krpmto55krpm (maximum speed 70krpm), with amplitudes and frequencies that correlate well with the test data. The comparisons validate the comprehensive rotor-bearings model whose ultimate aim is to save TC design time and accelerate product development.

Copyright © 2007 by American Society of Mechanical Engineers
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References

Figures

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Figure 1

Schematic view of an automotive turbocharger supported on floating ring bearings

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Figure 2

Automotive turbocharger: rotor assembly and floating ring bearings (FRBs)

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Figure 3

Structural FE model of turbocharger rotor and floating ring bearings. Locations of shaft motion measurements and mass imbalance planes noted. (Dimensions in m).

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Figure 4

Free–free mode shapes for turbocharger rotor—predictions and measurements at room temperature. (Dimensions in m).

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Figure 5

Floating ring speed ratios at turbine and compressor side bearings—predictions and measurements for 38°C oil inlet temperature and increasing feed pressures

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Figure 6

Predictions and measurements of lubricant exit temperature: 38°C lubricant inlet temperature and 206kPa feed pressure

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Figure 7

Predicted effective lubricant viscosity for inner and outer films of FRBs: 38°C lubricant inlet temperature, 206kPa supply pressure

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Figure 8

Waterfall of measured shaft motions at compressor and turbine ends of TC rotor: tests at 38°C lubricant inlet temperature and 206kPa supply pressure

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Figure 9

Predicted damped natural frequencies and associated mode shapes: 38°C lubricant inlet temperature, 206kPa supply pressure

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Figure 10

Measured and predicted synchronous (1X) motions at the turbine and compressor ends of TC rotor: lubricant at 38°C and 206kPa supply conditions

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Figure 11

Waterfall of predicted vertical shaft motions at the turbine and compressor ends of TC rotor. Lubricant at 38°C and 206kPa supply conditions

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Figure 12

Predicted and measured total shaft motion at the turbine and compressor ends of TC rotor: lubricant at 38°C and 206kPa supply conditions

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Figure 13

Amplitude of subsynchronous motions (Y direction) versus shaft speed at the compressor end of TC rotor: lubricant at 38°C and 206kPa supply conditions

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Figure 14

Amplitude of subsynchronous motions (Y direction) versus whirl frequency ratio at the compressor end of TC rotor: lubricant at 38°C and 206kPa supply conditions

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Figure 15

Predicted and measured subsynchronous whirl frequencies versus shaft speed (turbine and compressor rotor ends): lubricant at 38°C and 206kPa supply conditions

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