Research Papers: Gas Turbines: Structures and Dynamics

Impact of Screens Around Bearings on the Flow and Heat Transfer in the Vent and Scavenge Oil Pipes in Bearing Chambers

[+] Author and Article Information
Michael Flouros

 MTU Aero Engines, Dachauer Strasse 665, 80995 Munich, Germanymichael.flouros@mtu.de

Francois Cottier

 MTU Aero Engines, Dachauer Strasse 665, 80995 Munich, Germanyfrancois.cottier@mtu.de

J. Eng. Gas Turbines Power 133(3), 032503 (Nov 12, 2010) (10 pages) doi:10.1115/1.4002153 History: Received February 18, 2010; Revised June 22, 2010; Published November 12, 2010; Online November 12, 2010

The aim of this paper is to investigate, first, the effects of screens introduced around bearings and, second, the use of protruded instead of flush installed vent pipes. The investigation focuses on the air and oil flow distributions and on the heat transfer in the scavenge and the vent pipes in an aeroengine bearing chamber. The flow distribution has an impact on the pipe’s wall temperature distribution with the likelihood of generating hot spots. High temperatures may cause substantial effects on the health of the lubrication system. Problems may range from oil quality degradation to oil self ignition. A steady state CFD analysis of the heat transfer involving the two-phase air and oil flow in these pipes is performed using the ANSYS CFX package. It was demonstrated that whereas screens around bearings reduce the parasitic losses and vent protrusion reduces the oil flow to the air/oil separator, however, due to the oil flow distribution the thermal effects may lead to high material temperatures and to malfunctions in the engine’s lube system.

Copyright © 2011 by American Society of Mechanical Engineers
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Figure 1

(a) Schematic of the ATOS rig showing the screens (three types) and the protruding vent and (b) schematic of the CLEAN TCF with the secondary air system

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Figure 2

Parasitic power losses in a bearing chamber with and without screens surrounding the bearing (4-5)

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Figure 3

Oil quantity as a percentage of the base line flow leaving the bearing chamber through the vent pipe (4-5)

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Figure 4

Engine bearing chamber casing with a protruded vent and a snorkel

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Figure 5

(a) CAD model with the involved air streams for cooling and sealing and (b) wall and flow domain mesh

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Figure 6

Flow patterns in the vent (annular) and in the scavenge (bubbly) pipes

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Figure 7

Flow patterns in the vent (annular) and in the scavenge (bubbly) pipes

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Figure 8

Oil concentration (volume fraction) in the scavenge pipe from three viewing perspectives (a–c) corresponding to case No. 1 from Table 1. (d) Shows the oil concentration along the tube axis.

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Figure 9

Oil flow distribution in vicinity of the vent inner tube’s wall for cases 1, 2, and 4. The cross section shows that the core of the tube is almost oil free (case No. 1, No screens/flush vent). In the brackets the volumetric oil to air ratios for case 2 (screens/flush vent).

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Figure 10

Vent tube wall temperature distributions

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Figure 11

Scavenge tube wall temperature distributions

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Figure 12

Heat transfer coefficients in the vent tube against the Reynolds number for the oil




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