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Research Papers: Gas Turbines: Structures and Dynamics

Numerical Investigation of the Flow in a Hydrodynamic Thrust Bearing With Floating Disk

[+] Author and Article Information
Magnus Fischer

e-mail: magnus.fischer@ch.abb.com

Bruno Ammann

ABB Turbo Systems,
AG Baden, Switzerland

1Corresponding author.

Contributed by International Gas Turbine Institute (IGTI) division of ASME for publication in the Journal of Engineering for Gas Turbines and Power. Manuscript received July 27, 2012; final manuscript received August 9, 2012; published online January 8, 2013. Editor: Dilip R. Ballal.

J. Eng. Gas Turbines Power 135(2), 022502 (Jan 08, 2013) (10 pages) Paper No: GTP-12-1303; doi: 10.1115/1.4007775 History: Received July 27, 2012; Revised August 09, 2012

In this paper we present a novel method for the numerical simulation of flow in a hydrodynamic thrust bearing with floating disk. Floating disks are commonly employed in turbochargers and are situated between the thrust collar, which is rotating at turbocharger speed, and the static casing. A floating disk reduces wear, improves the skew compensating capacity of the bearing, and is freely movable in the axial direction. The simulation model presented combines a commercial flow solver (ANSYS CFX) with a control unit. Based on physical principles and a predefined axial thrust, the control unit automatically sets the rotational speed of the floating disk, the mass flow of the oil supply, and the oil film thickness between the rotating disk and the casing wall and collar, respectively. The only additional inputs required are the temperature and the pressure of the oil at the oil feed and the turbocharger speed. The width of the computational grid of the thin lubricating oil film in the gaps is adjusted using a mesh-morphing approach. The temperature-dependent variation in viscosity is included in the model. The calculated solution of the flow field in the domain, the oil film thickness, and the resulting rotational velocity of the floating disk are validated against experimental data and demonstrate favorable agreement. The influence of uncertainties in the measurements and the behavior of the systems are thoroughly investigated in parametric studies that reveal the key influencing factors. These are the temperature-dependent viscosity of the oil, the axial thrust, and turbulence effects in the supply grooves and ducts of the floating disk. Using the model presented here, it is now possible to predict design variants for this type of bearing.

Copyright © 2013 by ASME
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References

Dowson, D., 1962, “A Generalized Reynolds Equation for Fluid Film Lubrication,” Int. J. Mech. Sci.4, pp. 159–170. [CrossRef]
Dobrica, M. B., and Fillon, M., 2006, “Thermohydro-Dynamic Behavior of Slider Pocket Bearing, ASME J. Tribol., 128, pp. 312–318. [CrossRef]
Szeri, A. Z., 2011, Fluid Film Lubrication, 2nd ed., Cambridge University Press, Cambridge, U.K.
Medhioub, M., 2005, “Axialgleitlager bei hohen Umfangs-Geschwindigkeiten und Hohen Spezifischen Belastungen,” Dissertation, TU Braunschweig, Germany.
Yu, T. H., and Sadeghi, F., 2002, “Thermal Effects in Thrust Washer Lubrication,” ASME J. Tribol., 124(1), pp. 166–177. [CrossRef]
Kucinschi, B. R., DeWitt, K. J., and Pascovici, M. D., 2004, “Thermoelastohydrodynamic (TEHD) Analysis of a Grooved Thrust Washer,” ASME J. Tribol., 126(2), pp. 267–274. [CrossRef]
Chen, P. Y. P., and Hahn, E. J., 1998, “Use of Computational Fluid Dynamics in Hydrodynamic Lubrication,” P. I. Mech. Eng. J–J. Eng., 212(6), pp. 427–436. [CrossRef]
Guo, S., Hirano, T., and Kirk, R. G., 2003, “Application of CFD Analysis for Rotating Machinery: Part 1—Hydrodynamic, Hydrostatic Bearings and Squeeze Film Damper”, Proceedings of ASME Turbo Expo 2003, Atlanta, GA, June 16–19, ASME Paper No. GT2003-38931. [CrossRef]
Falz, E., 1931, Grundzuege der Schmiertechnik, Springer-Verlag, Berlin.
Menter, F., Carregal Ferreira, J., Esch, T., and Konno, B., 2003, “The SST Turbulence Model With Improved Wall Treatment for Heat Transfer Predictions in Gas Turbines,” Proceedings of the International Gas Turbine Congress 2003, Tokyo, November 2–7.

Figures

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Fig. 1

Schematic of the thrust bearing and the floating disk. Solid parts are indicated by numbers: bearing housing (1); floating disk (2); thrust collar (3); shaft (4); bearing collar (5). Fluid regions are defined with letters as follows: oil reservoir (a); oil supply lines (b); annular plenum (c); supply hole (d); lubricating groove, compressor-side (e); lubricating groove, turbine-side (f); gap, compressor-side (g); gap, turbine-side (h); floating disk journal bearing (i); annular gap (j); plenum (k).

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Fig. 2

The linear displacement function ξ for the gap on the compressor side

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Fig. 3

Typical convergence history during a computational run

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Fig. 4

Pressure and temperature field on the walls of the gap at the compressor side. Left: wall of the turbine housing. Right: wall of the floating disk. Top: pressure field. Bottom: temperature field.

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Fig. 5

Pressure, temperature, and velocity field on a cutting plane through the gap on the compressor side on a medium radius. At the bottom the radial velocity field is shown; vectors indicate the circumferential relative velocity.

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Fig. 6

Pressure and temperature field on the walls of the gap at the turbine side. Left: wall of the thrust collar. Right: wall of the floating disk. Top: pressure field. Bottom: temperature field.

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Fig. 7

Pressure, temperature, and velocity field on a cutting plane through the gap on the turbine side on a medium radius. The radial velocity field is shown at the bottom; vectors indicate the circumferential relative velocity.

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Fig. 8

Pressure and velocity field in cutting planes at the supply hole. At the top the axial velocity field is shown.

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Fig. 9

Calculated and experimentally obtained rotational speed of the floating disk versus turbocharger speed

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Fig. 10

Comparison between measured and calculated temperatures in the lubricating gap on the turbine side. Results are plotted for the three different operating points.

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Fig. 11

Oil film thickness on the turbine and compressor side of the thrust bearing versus turbocharger speed

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Fig. 12

Calculated mean lubricant temperature at the outlets of the lubricating gaps and the supply hole versus turbocharger speed

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Fig. 13

Mass flow through the thrust bearing for different operating points and a thrust variation

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Fig. 14

Floating disk speed for different axial thrust versus turbocharger speed

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Fig. 15

Width of the lubricating gaps on the turbine and compressor side of the floating disk for the three different operating points with a variation of the axial thrust

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Fig. 16

Mean lubricant temperature at the outlet of the lubricating gaps versus turbocharger speed for different axial thrusts

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