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Research Papers: Gas Turbines: Structures and Dynamics

Turbocharger Nonlinear Response With Engine-Induced Excitations: Predictions and Test Data

[+] Author and Article Information
Luis San Andrés, Ash Maruyama

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

Kostandin Gjika

 Honeywell Turbo Technologies, Zone Industrielle Inova 3000, 2 rue de l’Avenir, 88155 Thaon-les-Vosges Cedex, France

Sherry Xia

 Honeywell Turbo Technologies, No. 430 Li Bing Road, 201203 Shanghai, China

In the tests, the measurements of shaft displacements and TC housing acceleration were not recorded simultaneously.

The static play refers to the maximum diametral displacement of the shaft compressor wheel nose or nut of the rotating group determined from the output of the shaft motion measurement instrumentation by manually moving the rotating group through a conical motion.

These pressures change from their supply value measured upstream due to losses at the inlet port as well as centrifugal pressure losses due to the ring rotation and feed hole distribution and configuration.

It is not possible to replicate the test data as housing accelerations (center housing and compressor housing) were not collected simultaneously with shaft vibration measurements. Also, the frequency step size used (10 Hz) is too large and fails to capture the shaft vibration amplitudes at frequencies coinciding with exact orders of engine speed.

J. Eng. Gas Turbines Power 132(3), 032502 (Dec 01, 2009) (10 pages) doi:10.1115/1.3159368 History: Received March 21, 2009; Revised March 25, 2009; Published December 01, 2009; Online December 01, 2009

Turbochargers (TCs) aid to produce smaller and more fuel-efficient passenger vehicle engines with power outputs comparable to those of large displacement engines. This paper presents further progress on the nonlinear dynamic behavior modeling of rotor-radial bearing system by including engine-induced (TC casing) excitations. The application is concerned with a semifloating bearing design commonly used in high speed turbochargers. Predictions from the model are validated against test data collected in an engine-mounted TC unit operating at a top speed of 160 krpm (engine speed=3600rpm). The bearing model includes noncylindrical lubricant films as in a semifloating-ring bearing with an antirotation button. The nonlinear rotor transient response model presently includes input base motions for the measured TC casing accelerations for increasing engine load conditions. Engines induce TC casing accelerations rich in multiple harmonic frequencies; amplitudes being significant at two and four times the main engine speed. Fast Fourier transfor frequency domain postprocessing of predicted nonlinear TC shaft motions reveals a subsynchronous whirl frequency content in good agreement with test data, in particular, for operation at the highest engine speeds. Predicted total shaft motion is also in good agreement with test data for all engine loads and over the operating TC shaft speed range. The comparisons validate the rotor-bearing model and will aid in reducing product development time and expenditures.

Copyright © 2010 by American Society of Mechanical Engineers
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References

Figures

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Figure 1

Turbocharger rotor assembly with SFRB support

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Figure 2

Turbocharger rotor and semifloating-ring bearing structural models

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Figure 3

Measured and predicted first and second free-free natural frequency mode shapes of TC rotor at room temperature

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Figure 4

Turbocharger engine test facility stand

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Figure 5

Waterfalls of center housing (top) and compressor housing (bottom) acceleration test data versus orders of engine frequency (100% engine load, vertical direction)

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Figure 6

Peak acceleration of TC center housing and compressor housing versus engine speed (100% load, measurements along vertical direction)

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Figure 7

Depiction of TC center housing motions for rotordynamics analysis (taken from Ref. 15)

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Figure 8

TC-SFRB system damped natural frequency map for 100% engine load

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Figure 9

Predicted rotor-SFRB natural mode shapes at 80 krpm (100% engine load)

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Figure 10

Waterfalls of shaft motion (compressor nose, vertical direction). Predictions with no housing accelerations (top), predictions with housing accelerations (middle), and test data (bottom) (100% engine load)

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Figure 11

Total TC shaft motion amplitude, predicted and measured, versus shaft speed (100% engine load)

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Figure 12

Predicted and measured subsynchronous shaft motion amplitudes versus engine speed (compressor nose, vertical direction)

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Figure 13

Predicted and measured subsynchronous shaft motion amplitudes versus orders of engine speed (compressor nose, vertical direction)

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Figure 14

Predicted and measured shaft subsynchronous whirl frequencies versus shaft speed (compressor nose, vertical direction, 100% IC engine load)

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Figure 15

Predicted and measured subsynchronous whirl frequencies versus engine speed (compressor nose, vertical direction, 100% IC engine load)

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Figure 16

Predicted exit inner and outer film temperatures at compressor bearing for 25%, 50%, and 100% engine loads

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Figure 17

Predicted effective lubricant film viscosities of the compressor bearing end for 25% 50%, and 100% engine loads

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Figure 18

Predicted inner and outer film clearances relative to nominal cold radial clearances of the compressor bearing end for 25%, 50%, and 100% engine loads

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