A detailed computational study of the air-flow through the outer gap of the front bearing of an aero-engine is presented. The reason to carry out this study was to understand the flow through the bearing as a function of the operational parameters of the engine, which was necessary for the modeling of the flow in the whole bearing chamber. The complex geometry and the size of the bearing gap relative to the overall dimensions of the bearing chamber and the need for very precise and detailed information of the effect on the flow within the chamber of the bearing operational parameters, prohibited the solution of the flow through the gap together with the rest of the bearing chamber. A 3D modeling of the flow through the outer bearing gap, which included a section of the ball bearing, was performed. Functions relating the pressure drop of the air coming through the bearing gap and the tangential component of velocity of the air exiting the bearing region, to the mass of air through the gap of the ball bearing and the rotational speed of the shaft were developed. The effect of the lubrication oil within the bearing was modeled as an anisotropic porous medium with a predefined law. In order to acquire in a mathematical form the above relationships a series of computational runs were performed. These relationships, in the form of second order curves, were subsequently introduced to the model of the bearing chamber as described by Aidarinis and Goulas (2014, “Enhanced CFD Modeling and LDA Measurements for the Air-Flow in an Aero Engine Front Bearing Chamber (Part I),” ASME Paper No. GT2014-26060). The constants of the relationships were derived through comparisons of the calculations with the experimental data. From the analysis, it was concluded that the pressure drop across the bearing increases with the square of the rotational speed of the shaft with the mass flow of air through the ball bearing as a parameter and vice versa. For this particular ball bearing, there is a region where, for any combination of rotational speed of the shaft and pressure drop through the bearing, there is no flow of air through the bearing. In this paper the detailed modeling methodology, the computational flow field, the boundary conditions and finally the results are presented and discussed.

## References

1.
Gorse
,
P.
,
Dullenkopf
,
K.
, and
Bauer
,
H.-J.
,
2005
, “
The Effect of Airflow Across Aero-Engine Roller Bearing on Oil Droplet Generation
,” 17th International Symposium on Air Breathing Engines, Munich, Germany, Sept. 4–9, Paper No. 2005-1208.
2.
Flouros
,
M.
,
2005
, “
The Impact of Oil and Sealing Air Flow, Chamber Pressure, Rotor Speed, and Axial Load on the Power Consumption in an Aeroengine Bearing Chamber
,”
ASME J. Eng. Gas Turbines Power
,
127
(
1
), pp.
182
186
.10.1115/1.1805009
3.
Flouros
,
M.
,
2006
, “
Reduction of Power Losses in Bearing Chambers Using Porous Screens Surrounding the Ball Bearing
,”
ASME J. Eng. Gas Turbines Power
,
128
(
1
), pp.
178
182
.10.1115/1.1995769
4.
Gorse
,
P.
,
Dullenkopf
,
K.
,
Bauer
,
H.-J.
, and
Wittig
,
S.
,
2008
, “
An Experimental Study on Droplet Generation in Bearing Chambers Caused by Roller Bearings
,”
ASME
Paper No. GT2008-51281.10.1115/GT2008-51281
5.
Wang
,
Y.
,
Hibberd
,
S.
,
Simmons
,
K.
,
Eastwick
,
C.
, and
Care
,
I.
,
2001
, “
Application of CFD to Modelling Two-Phase Flow in a High-Speed Aero-Engine Transmission Chamber
,”
ASME Fluids Engineering Division Summer Meeting
, New Orleans, LA, May 29–June 1, pp.
249
254
.
6.
Farrall
,
M.
,
Hibberd
,
S.
, and
Simmons
,
K.
,
2003
, “
Modelling Oil Droplet/Film Interaction in an Aero-Engine Bearing Chamber
,” 9th International Conference on Liquid Atomization and Spray Systems (ICLASS 2003), Sorrento, Italy, July 13–18.
7.
Farrall
,
M. B.
,
Hibberd
,
S.
, and
Simmons
,
K.
,
2000
, “
Computational Modelling of Two-Phase Air/Oil-Flow Within an Aero-Engine Bearing Chamber
,”
ASME Fluids Engineering Division Summer Meeting
, Boston, MA, June 11–15.
8.
Lee
,
C. W.
,
Palma
,
P. C.
,
Simmons
,
K.
, and
Pickering
,
S. J.
,
2005
, “
Comparison of Computational Fluid Dynamics and Particle Image Velocimetry Data for the Airflow in an Aeroengine Bearing Chamber
,”
ASME J. Eng. Gas Turbines Power
,
127
(
4
), pp.
697
703
.10.1115/1.1924635
9.
Aidarinis
,
J.
,
Missirlis
,
D.
,
Yakinthos
,
K.
, and
Goulas
,
A.
,
2011
, “
CFD Modeling and LDA Measurements for the Air-Flow in an Aero Engine Front Bearing Chamber
,”
ASME J. Eng. Gas Turbines Power
,
133
(
8
), p.
082504
.10.1115/1.4002830
10.
ANSYS, 2010, ANSYS FLUENT 13.0 Documentation, ANSYS Inc., Canonsburg, PA.
11.
Aidarinis
,
I.
,
2011
, “
CFD Modeling and Experimental Study of the Flow in Aero Engine Bearing Chambers
,” Ph.D. thesis, Aristotle University of Thessaloniki, Thessaloniki, Greece.
12.
Aidarinis
,
J.
, and
Goulas
,
A.
,
2014
, “
Enhanced CFD Modeling and LDA Measurements for the Air-Flow in an Aero Engine Front Bearing Chamber—Part I
,”
ASME
Paper No. GT2014-26060.10.1115/GT2014-26060