Within the compression system of a gas turbine engine a significant amount of air is removed to fulfill various requirements associated with cooling, ventilation, and sealing. Flow is usually removed through off-takes located in regions where space is restricted, while the flow is highly complex containing blade wakes, secondary flows, and other flow features. This paper investigates the performance of a pitot style off-take aimed at providing a high pressure recovery in a relatively short length. For this to be achieved some prediffusion of the flow is required upstream of the off-take (i.e., by making the off-take larger than the captured streamtube). Although applicable to a variety of applications, the system is targeted at an intercooled aero-engine concept where the off-take would be located aft of the fan outlet guide vane (OGV) root and provide coolant flow to the heat exchangers. Measurements and numerical predictions are initially presented for a baseline configuration with no off-take present. This enabled the OGV near field region to be characterized and provided a datum, relative to which the effects of introducing an off-take could be assessed. With the off-take present a variety of configurations were investigated including different levels of prediffusion, prior to the off-take, and different off-take positions. For very compact systems of short length, such that the gap between the OGV and off-take is relatively small, the amount of prediffusion achievable is limited by the off-take pressure field and its impact on the upstream OGV row. This pressure field is also influenced by parameters such as the nondimensional off-take height and splitter thickness. The paper analyses the relative importance of these various effects in order to provide some preliminary design rules. For systems of increased length a significant amount of flow prediffusion can be achieved with little performance penalty. However, the prediffusion level is eventually limited by the increased distortion and pressure losses associated with the captured streamtube.

References

References
1.
Walker
,
A. D.
,
Denman
,
P. A.
, and
McGuirk
,
J. J.
,
2004
, “
Experimental and Computational Study of Hybrid Diffusers for Gas Turbine Combustors
,”
ASME J. Eng. Gas Turbines Power
,
126
(
4
), pp.
717
725
.10.1115/1.1772403
2.
Merchant
,
A.
,
2003
, “
Aerodynamic Design and Performance of Aspirated Airfoils,
ASME J. Turbomach.
,
125
(
1
), pp.
141
148
.10.1115/1.1519834
3.
ESDU
, “
Estimation of Spillage Drag for a Wide Range of Axisymmetric Intakes at M<1
,”
June 1984 ESDU Data sheet 84004a
.
4.
ESDU
, “
Drag and Pressure Recovery Characteristics of Auxiliary Air Inlets at Subsonic Speeds
,”
April 1983 ESDU Data sheet 86002
.
5.
Barker
,
A. G.
, and
Carrotte
,
J. F.
,
2001
, “
‘Influence of Compressor Exit Conditions on Annular Diffusers Part I: Diffuser Performance
,”
J. Propul. Power
,
17
(
3
), pp.
678
686
.10.2514/2.5795
6.
Barker
,
A. G.
, and
Carrotte
,
J. F.
,
2001
, “
Influence of Compressor Exit Conditions on Annular Diffusers Part II: Flow Redistribution
,”
J. Propul. Power
,
17
(
3
), pp.
687
694
.10.2514/2.5796
7.
Stevens
,
S. J.
,
Harasgama
,
S. P.
, and
Wray
,
A. P.
,
1984
, “
Influence of Blade Wakes on the Performance of Combustor Shortened Prediffusers
,”
J. Aircraft
,
21
(
9
), pp.
641
648
.10.2514/3.45009
8.
Wilfert
,
G.
,
Sieber
,
J.
,
Rolt
,
A.
,
Baker
,
N.
,
Touyeras
,
A.
, and
Colantuoni
,
S.
,
2007
, “
New Environmental Friendly Aero Engine Core Concepts
,”
XVIII International Symposium on Air Breathing Engines (ISABE 2007), Beijing, China, September 2–7, Paper No. ISABE-2007-1120
.
9.
Rolt
,
A.
, and
Baker
,
N.
,
2009
, “
Intercooled Turbofan Engine Design and Technology Research in the EU Framework 6 NEWAC Programme
,”
XIX International Symposium on Air Breathing Engines 2009 (ISABE 2009), Montreal, Canada, September 7–11, Paper No. ISABE-2009-1278
.
10.
Cumpsty
,
N. A.
,
1989
,
Compressor Aerodynamics
,
Longman Scientific and Technical
,
Harlow, UK
.
11.
Wray
,
A. P.
, and
Carrotte
,
J. F.
,
1993
, “
The Development of a Large Annular Facility for Testing Gas Turbine Combustor Diffuser Systems
,”
Paper No. AIAA-93-2546
.
12.
Fishenden
,
C. R.
, and
Stevens
,
S. J.
,
1997
, “
Performance of Annular Combustor-Dump Diffusers
,”
J. Aircraft
,
14
(
1
), pp.
60
67
.10.2514/3.58749
13.
Livesey
,
J. L.
,
1972
, “
Duct Performance Parameters Considering Spatially Non-Uniform Flows
,”
American Institute of Aeronautics and Astronautics, 10th Aerospace Sciences Meeting, San Diego, CA, January 17–19, Paper No. AIAA-1972-85
.
14.
Denton
,
J. D.
,
1993
, “
Loss Mechanisms in Turbomachinery
,”
ASME J. Turbomach.
,
115
(
4
), pp.
621
656
.10.1115/1.2929299
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