Research Papers: Gas Turbines: Structures and Dynamics

Analysis of Thrust Bearing Impact on Friction Losses in Automotive Turbochargers

[+] Author and Article Information
Bjoern Hoepke

Institute for Combustion Engines,
RWTH Aachen University,
Forckenbeckstraße 4,
Aachen 52074, Germany
e-mail: hoepke@vka.rwth-aachen.de

Tolga Uhlmann

Neuenhofstrasse 181,
Aachen 52078, Germany
e-mail: uhlmann@fev.com

Stefan Pischinger

Institute for Combustion Engines,
RWTH Aachen University,
Forckenbeckstraße 4,
Aachen 52074, Germany
e-mail: pischinger@vka.rwth-aachen.de

Bernhardt Lueddecke

IHI Charging Systems International GmbH,
Haberstrasse 3+24,
Heidelberg 69126, Germany
e-mail: b.lueddecke@ihi-csi.de

Dietmar Filsinger

IHI Charging Systems International GmbH,
Haberstrasse 3+24,
Heidelberg 69126, Germany
e-mail: d.filsinger@ ihi-csi.de

Contributed by the Structures and Dynamics Committee of ASME for publication in the JOURNAL OF ENGINEERING FOR GAS TURBINES AND POWER. Manuscript received October 31, 2014; final manuscript received December 12, 2014; published online February 3, 2015. Editor: David Wisler.

J. Eng. Gas Turbines Power 137(8), 082507 (Aug 01, 2015) (8 pages) Paper No: GTP-14-1598; doi: 10.1115/1.4029481 History: Received October 31, 2014; Revised December 12, 2014; Online February 03, 2015

The importance of automotive turbocharger performance is continuously increasing. However, further gains in efficiency are becoming progressively difficult to achieve. The bearing friction losses impact the overall efficiency of the turbocharger and accordingly the understanding of bearing systems and their characteristics is essential for future improvements. In this work, a detailed analysis on the mechanical losses occurring in the bearing system of automotive turbochargers is presented. Friction losses have been measured experimentally on a special test bench up to rotational speeds of nTC = 130,000 1/min. Special interest was given to the thrust bearing characteristics and its contribution to the total friction losses. For this, the experiments were split into three parts: first, friction power was determined as a function of turbocharger speed at zero externally applied thrust load. Second, external thrust load up to 40 N was applied onto the turbocharger bearing at fixed rotational speeds of nTC = 40,000, 80,000, and 120,000 1/min. Increasing thrust load was observed to result in increasing friction losses amounting to a maximum of 32%. At last, a specially prepared turbocharger center section with deactivated thrust bearing was investigated. A comparison of these results with the measurement of the conventional bearing system under thrust-free conditions allowed separating journal and thrust bearing losses. The contribution of the thrust bearing to the overall bearing losses appeared to be as high as 38%. Furthermore, a modeling approach for estimating the friction power of both fully floating journal bearing as well as thrust bearing is illustrated. This theoretical model is shown to predict friction losses reasonably well compared to the experimental results.

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Fig. 1

Schematic Stribeck curve

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Fig. 2

Schematic of journal bearing geometry and film pressure distribution

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Fig. 3

Schematic of thrust bearing geometry and film pressure distribution

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Fig. 4

Setup of motoring TC friction test bench

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Fig. 5

Installation of tested turbocharger on the test bench

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Fig. 6

Normalized total friction losses as a function of turbocharger speed

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Fig. 7

Normalized total friction power as a function of thrust load for constant speed

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Fig. 8

Comparison of normalized friction power with and without thrust bearing as a function of speed

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Fig. 9

Process diagram of journal bearing model

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Fig. 10

Results of journal bearing modeling

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Fig. 11

Schematic of double-sided thrust bearing

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Fig. 12

Results of thrust bearing modeling for nTC = 80,000 1/min

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Fig. 13

Quantification of thrust bearing impact on overall bearing friction loss for nTC = 80,000 1/min




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