Research Papers: Gas Turbines: Structures and Dynamics

CFD Modeling and LDA Measurements for the Air-Flow in an Aero Engine Front Bearing Chamber

[+] Author and Article Information
J. Aidarinis, D. Missirlis, K. Yakinthos, A. Goulas

Laboratory of Fluid Mechanics and Turbomachinery, Department of Mechanical Engineering, Aristotle University of Thessaloniki, Egnatia Street, 54124 Thessaloniki, Greece

J. Eng. Gas Turbines Power 133(8), 082504 (Apr 08, 2011) (8 pages) doi:10.1115/1.4002830 History: Received July 06, 2010; Revised July 19, 2010; Published April 08, 2011; Online April 08, 2011

The continuous development of aero engines toward lighter but yet more compact designs, without decreasing their efficiency, has led to gradually increasing demands on the lubrication system, such as the bearing chambers of an aero engine. For this reason, it is of particular importance to increase the level of understanding of the flow field inside the bearing chamber in order to optimize its design and improve its performance. The flow field inside a bearing chamber is complicated since there is a strong interaction between the sealing air-flow and the flow of lubrication oil, and both of them are affected by and interacting with the geometry of the chamber and the rotating shaft. In order to understand the flow field development and, as a next step, to optimize the aero engine bearing chamber performance, in relation to the lubrication and heat transfer capabilities, the behavior of this interaction must be investigated. In this work, an investigation of the air-flow field development inside the front bearing chamber of an aero engine is attempted. The front bearing chamber is divided into two separate sections. The flow from the first section passes through the bearing and the bearing holding structure to the second one where the vent and the scavenging system are located. The investigation was performed with the combined use of experimental measurements and computational fluid dynamics (CFD) modeling. The experimental measurements were carried out using a laser Doppler anemometry system in an experimental rig, which consists of a 1:1 model of the front bearing chamber of an aero engine. Tests were carried out at real operating conditions both for the air-flow and for the lubricant oil-flow and for a range of shaft rotating speeds. The CFD modeling was performed using a commercial CFD package. Particularly, the air-flow through the bearing itself was modeled, adopting a porous medium technique, the parameters of which were developed in conjunction with the experiments. A satisfactory quantitative agreement between the experimental measurements and the CFD computations was achieved. At the same time, the effect of the important parameters such as the air and oil mass flow, together with the shaft rotational speed, and the effect of the chamber geometry were identified. The conclusions can be exploited in future attempts in combination with the CFD model developed in order to optimize the efficiency of the lubrication and cooling system. The latter forms the main target of this work, which is the development of a useful engineering tool capable of predicting the flow field inside the aero engine bearing, which can be used subsequently for optimization purposes.

Copyright © 2011 by American Society of Mechanical Engineers
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Figure 8

Typical plots of the CFD computations. (a) Axial velocity contour 4000 rpm and mg=23 g/s. (b) Axial velocity contour 5500 rpm and mg=33 g/s. (c) Axial velocity contour 4000 rpm and mg=23 g/s. (d) Axial velocity contour 5500 rpm and mg=33 g/s. (e) Negative velocity isosurfaces 4000 rpm and mg=23 g/s. (f) Velocity magnitude streamlines 5500 rpm and mg=33 g/s.

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Figure 1

Bearing chamber test rig (a) general view and (b) enlarged view in the bearing cage region

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Figure 2

Bearing chamber test rig cross section design

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Figure 3

Bearing chamber experimental test facilities

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Figure 4

Measurement position inside the bearing chamber

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Figure 5

Computational domain and measurement grid position inside the bearing chamber

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Figure 6

Bearing chamber computational grid

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Figure 7

Axial velocity comparison between LDA measurements and CFD results. (a) 5500 rpm, mg=33 g/s, x=163.5 mm, and y=55 mm. (b) 4000 rpm, mg=23 g/s, x=163.5 mm, and y=55 mm. (c) 4000 rpm, mg=33 g/s, x=163.5 mm, and y=75 mm. (d) 5500 rpm, mg=23 g/s, x=143.5 mm, and y=55 mm.



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