TECHNICAL PAPERS: Gas Turbines: Structures and Dynamics

Reduction of Power Losses in Bearing Chambers Using Porous Screens Surrounding a Ball Bearing

[+] Author and Article Information
Michael Flouros

MTU Aeroengines, Air and Oil Systems, Dachauer Strasse 665, 80995 Munich, Germanymichael.flouros@muc.mtu.de

J. Eng. Gas Turbines Power 128(1), 178-182 (May 01, 2005) (5 pages) doi:10.1115/1.1995769 History: Received April 02, 2004; Revised May 01, 2005

Trends in aircraft engine design have caused an increase in mechanical stress requirements for rolling bearings. Consequently, a high amount of heat is rejected, which results in high oil scavenge temperatures. An RB199 turbofan bearing and its associated chamber were modified to carry out a survey aiming to reduce power losses in bearing chambers. The test bearing was a 124 mm PCD ball bearing with a split inner ring employing under-race lubrication by two individual jets. The survey was carried out in two parts. In the first part, the investigations were focused on the impact on the power losses in the bearing chamber of the operating parameters, such as oil flow, oil temperature, sealing air flow, bearing chamber pressure, and shaft speed. In the second part, the investigations focused on the reduction of the dwell time of the air and oil mixture in the bearing compartment and its impact on the power losses. In this part, porous screens were introduced around the bearing. These screens would aid the oil to flow out of the compartment and reduce droplet-droplet interactions as well as droplet-bearing chamber wall interactions. The performance of the screens was evaluated by torque measurements. A high-speed camera was used to visualize the flow in the chamber. Considerable reduction in power loss was achieved. This work is part of the European Research programme GROWTH ATOS (Advanced Transmission and Oil Systems).

Copyright © 2006 by American Society of Mechanical Engineers
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Figure 1

Schematic of the bearing chamber with the rear and front nozzles, the endoscope, the thermocouple positions adjacent to the bearing, and the immersed vent

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Figure 2

Schematic of the test facility with the test bearing and the axial load arrangement

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Figure 3

Bearing chamber with the high-speed camera, endoscope, and purge facility

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Figure 4

Screens used at the front side of the ball bearing

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Figure 5

Rear and front screen arrangement

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Figure 6

Impact of screens as a function of the oil and air flow. The presence of screens results in significantly lower power loss to the bearing compartment.

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Figure 7

Impact of screens on the power loss as a function of shaft speed, PD, DSC, and temperature

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Figure 8

Oil exiting the bearing between cage and outer ring at 15,000 rpm, 200 L/H

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Figure 9

View of the front screen with the nonrotating bearing behind it

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Figure 10

Comparison of the spay generation between the basic configuration and the screens at 360 fps. Less spray is created when screens are used.

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Figure 11

High-speed camera images showing liquid oil emerging through the pores

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Figure 12

Vent-oil quantity measurements at different bearing and vent configurations, sealing air flows and shaft speeds. Screens always result to lower vent-oil quantity.



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