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Research Papers: Gas Turbines: Structures and Dynamics

Enhanced Computational Fluid Dynamics Modeling and Laser Doppler Anemometer Measurements for the Air-Flow in an Aero-engine Front Bearing Chamber—Part I

[+] Author and Article Information
J. Aidarinis

Laboratory of Fluid Mechanics
and Turbomachinery,
Aristotle University of Thessaloniki,
Egnatia Street,
Thessaloniki 54124, Greece
e-mail: aidarini@auth.gr

A. Goulas

Laboratory of Fluid Mechanics
and Turbomachinery,
Aristotle University of Thessaloniki,
Egnatia Street,
Thessaloniki 54124, Greece
e-mail: goulas@auth.gr

Contributed by the Structures and Dynamics Committee of ASME for publication in the JOURNAL OF ENGINEERING FOR GAS TURBINES AND POWER. Manuscript received August 20, 2014; final manuscript received October 27, 2014; published online January 28, 2015. Editor: David Wisler.

J. Eng. Gas Turbines Power 137(8), 082501 (Aug 01, 2015) (14 pages) Paper No: GTP-14-1500; doi: 10.1115/1.4029272 History: Received August 20, 2014; Revised October 27, 2014; Online January 28, 2015

Modern aero-engine development requires also a gradual increase in the overall effectiveness of lubrication systems. This particularly applies to bearing chambers where a complex two-phase flow is formed by the interaction of the sealing air and the lubrication oil. It is important to increase the level of understanding of the flow field inside the bearing chamber and to develop engineering tools in order to optimize its design and improve its performance. To achieve this, an experimental and a computational study of the whole front bearing chamber were carried out for a range of shaft rotational speeds and sealing air mass flow. The experimental measurements of the air velocity inside the chamber were carried out using a laser Doppler anemometer (LDA) in two-phase air/oil-flow conditions. The experimental facility is a 1:1 scale model of the front bearing chamber of an aero-engine. Computational 3D modeling of the bearing chamber was performed. The bearing gap and the presence of lubrication oil were modeled as an anisotropic porous medium with functions relating the pressure loss of the air coming through the gap and the tangential component of velocity of the air exiting the gap of the ball bearing with the air-flow rate through the gap and the rotational speed of the shaft. The methodology to obtain the above mentioned functions and the results of the detailed study are given (Aidarinis, J., and Goulas, A., 2014, “Enhanced CFD Modeling and LDA Measurements for the Air-Flow in an Aero Engine Front Bearing Chamber: Part II,” ASME Paper No. GT2014-26062). The enhanced computational model of the chamber implementing the law of pressure drop of the “lubricated” bearing and the function of modeling the tangential velocity of the air exiting the bearing was used to calculate the flow field for the full range of the measurements. A limiting curve dividing the operational map of the bearing chamber into two areas was predicted. Large vortical and swirling structures dominate the flow and they vary in size according to the position of the operation point relative to the limiting curve. Operation above the limiting curve leads to flow classified as type I with air going through the ball bearing while for operation below the limiting curve line the flow is classified as type II, there is no air-flow through the bearing gap.

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References

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Figures

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Fig. 1

Co-axial sectional view of the LFMT bearing chamber test rig

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Fig. 2

View of the measurement section in the chamber downstream the bearing

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Fig. 3

Distribution of axial velocity measurement points for 4000 rpm and 23/33 g/s (X = 60 mm)

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Fig. 4

Axial velocity profiles development and comparison for all measured cases at X = 20–140 mm

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Fig. 5

Axial velocity contours at 33.75 deg for 4000 rpm

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Fig. 6

Axial velocity contours at 33.75 deg for 5500 rpm

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Fig. 7

Axial velocity contours at 33.75 deg for 7000 rpm

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Fig. 8

Axial velocity contours and isosurface for Ux = 0, and −1 m/s for air mass flow 23 g/s and 4000/5500 rpm

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Fig. 9

Axial velocity contours and isosurfaces for Ux = 0, and − 1 m/s for air mass flow 33 g/s and 4000/5500 rpm

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Fig. 10

Axial velocity contours and isosurfaces for Ux = 0, and −1 m/s for air mass flow 23 g/s and 7000 rpm

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Fig. 11

Computational domain

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Fig. 12

3D computational grid

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Fig. 13

Plane Y = 0 mm for 4000 rpm and 23 g/s: (a) vector plots, (b) axial velocity, (c) circumferential velocity, and (d) circumferential velocity near the wall (5 mm)

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Fig. 14

Plane Y = 0 mm for 7000 rpm and 23 g/s: (a) vector plots, (b) axial velocity, (c) circumferential velocity, and (d) circumferential velocity near the wall (5 mm)

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Fig. 15

Vector plots for air mass flow rate 23 g/s and rotational speed: (a) 4000 and (b) 7000 rpm (planes Υ = 0 mm, Ζ = 0 mm)

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Fig. 16

Contours of axial velocity for air mass flow rate 33 g/s and (a) 4000, (b) 7000, (c) 10,000, and (d) 13,000 rpm of the shaft

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Fig. 17

Contours of circumferential velocity for air mass flow rate 33 g/s and (a) 4000, (b) 7000, (c) 10,000, and (d) 13,000 rpm

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Fig. 18

Contours of axial velocity for rotational speed 7000 rpm and air mass flow rate (a) 15, (b) 23, (c) 33, and (d) 50 g/s

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