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Research Papers: Hydrodynamic Lubrication

Computational Fluid Dynamics Thermohydrodynamic Analysis of Three-Dimensional Sector-Pad Thrust Bearings With Rectangular Dimples

[+] Author and Article Information
L. Kaiktsis

School of Naval Architecture and
Marine Engineering,
National Technical University of Athens,
Zografos 15710, Greece

M. Fillon

Institut Pprime,
Dept GMSC, CNRS
University of Poitiers,
ISAE-ENSMA,
Futuroscope Chasseneuil 86062, France

Contributed by the Tribology Division of ASME for publication in the JOURNAL OF TRIBOLOGY. Manuscript received February 22, 2013; final manuscript received August 2, 2013; published online October 3, 2013. Assoc. Editor: Robert L. Jackson.

J. Tribol 136(1), 011702 (Oct 03, 2013) (11 pages) Paper No: TRIB-13-1051; doi: 10.1115/1.4025245 History: Received February 22, 2013; Revised August 02, 2013

The paper presents a detailed computational study of flow patterns and performance indices in a dimpled parallel thrust bearing. The bearing consists of eight pads; the stator surface of each pad is partially textured with rectangular dimples, aiming at maximizing the load carrying capacity. The bearing tribological performance is characterized by means of computational fluid dynamics (CFD) simulations, based on the numerical solution of the Navier–Stokes and energy equations for incompressible flow. Realistic boundary conditions are implemented. The effects of operating conditions and texture design are studied for the case of isothermal flow. First, for a reference texture pattern, the effects of varying operating conditions, in particular minimum film thickness (thrust load), rotational speed and feeding oil pressure are investigated. Next, the effects of varying texture geometry characteristics, in particular texture zone circumferential/radial extent, dimple depth, and texture density on the bearing performance indices (load carrying capacity, friction torque, and friction coefficient) are studied, for a representative operating point. For the reference texture design, the effects of varying operating conditions are further investigated, by also taking into account thermal effects. In particular, adiabatic conditions and conjugate heat transfer at the bearing pad are considered. The results of the present study indicate that parallel thrust bearings textured by proper rectangular dimples are characterized by substantial load carrying capacity levels. Thermal effects may significantly reduce load capacity, especially in the range of high speeds and high loads. Based on the present results, favorable texture designs can be assessed.

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Figures

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Fig. 1

Top view sketch of the eight-pad thrust bearing of the present study

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Fig. 2

(a) Geometry of a partially textured bearing pad. (b) Corresponding geometry, flow boundary conditions, and discretization details of the fluid domain. (c) Convergence study (load carrying capacity, maximum pad temperature, and friction torque versus total number of nodes), for a representative case, taking into account thermal effects.

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Fig. 3

Validation study. (a) Geometry of the bearing pad utilized for validation tests. (b)–(d) Computed values of integral flow quantities, for bearing operation at 2600 rpm, for the present and previous studies: (b) minimum film thickness versus bearing load, (c) maximum pad temperature versus bearing load, and (d) minimum film thickness versus friction torque.

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Fig. 4

Reference case (N = 5000 rpm, hmin = 30 μm): Color-coded contours of (a) pressure and (b) wall shear stress on the rotor surface of a dimpled bearing pad. Isothermal flow is assumed.

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Fig. 5

Reference case (N = 5000 rpm, hmin = 30 μm): Pressure profiles at the three sectors depicted in Fig. 2. Isothermal flow is assumed.

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Fig. 6

(a) and (b) Computed values of load carrying capacity, friction torque, and normalized friction coefficient versus rotational speed and minimum film thickness, for a dimpled bearing pad. The independent parameters are varied around the reference case values. (c) Load carrying capacity versus rotational speed for the reference textured pad of the present work, and for an optimal tapered-land pad with the same principal dimensions, depicted in (d). In all cases, isothermal flow is assumed.

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Fig. 7

Computed values of load carrying capacity, friction torque, and normalized friction coefficient versus feeding pressure, for a dimpled bearing pad. Isothermal flow is assumed.

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Fig. 8

Computed values of normalized load carrying capacity, friction torque, and friction coefficient versus (a) circumferential texture angle, (b) texture radial width, (c) texture depth, and (d) texture density, for a dimpled bearing pad. Isothermal flow is assumed, while the independent parameters are varied around the reference case values.

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Fig. 9

Pressure profiles at the bearing midsector, on the rotor surface, for different values of circumferential texture angle at. Isothermal flow is assumed, while at is varied around the value corresponding to maximum W (Fig. 8(a)).

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Fig. 10

Color-coded contours of pressure on the rotor surface of a dimpled bearing pad, for different values of texture radial width: (a) Bt = 13 mm, (b) Bt = 15 mm (reference case), (c) Bt = 17 mm, and (d) Bt = 19 mm. Isothermal flow is assumed.

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Fig. 11

Pressure profiles along the pad midsector, for three values of dimple depth hd. Isothermal flow is assumed, while hd is varied around the value corresponding to maximum W (Fig. 8(c)).

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Fig. 12

(a), (c), (e), and (g) Load carrying capacity versus rotational speed, for isothermal flow, flow with conjugate heat transfer on the bearing pad and adiabatic flow, at different values of minimum film thickness. (b), (d), (f), and (h) Corresponding maximum computed fluid temperatures.

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Fig. 13

Operating conditions: hmin = 20 μm, N = 3000 rpm. The reference texture design is implemented, and flow with conjugate heat transfer on the bearing pad is considered. (a) Fluid temperature distribution at the film midplane (10 μm from the rotor surface), (b) corresponding viscosity distribution, and (c) temperature distribution at the bearing pad.

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Fig. 14

Operating conditions: hmin = 20 μm, N = 3000 rpm. Color-coded contours of pressure on the rotor surface of a dimpled bearing pad, for different problem setups: (a) isothermal flow, and (b) flow with conjugate heat transfer on the bearing pad.

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