In high-efficiency gas turbine engines, the cooling air for the high-pressure turbine stage is expanded through stationary preswirl nozzles, transferred through the preswirl chamber, and delivered to the blade feed holes of the rotor. By accelerating the cooling air in the direction of rotation, the total temperature relative to the rotor disk and the pressure losses occurring at the receiver hole inlet can be reduced. The discharge behavior of a direct-transfer preswirl system has been investigated experimentally for different number of receiver holes and different inlet geometries, varying axial gap widths between stator and rotor and for rotational Reynolds numbers up to $Reϕ=2.3×10 6.$ The discharge coefficients of the preswirl nozzles are given in the absolute frame of reference while the definition of the discharge coefficients of the receiver holes is applied to the rotating system in order to consider the work done by the rotor. A momentum balance is used to evaluate the deflection of the preswirled air entering the receiver holes. The flow in the preswirl chamber is characterized by introducing an effective velocity of the cooling air upstream of the rotor disk. The influences of geometrical parameters and operating points are reported and discussed in this paper.

1.
Scricca, J. A., and Moore, K. D., 1997, “Effects of ‘Cooled’ Cooling Air on Pre-Swirl Nozzle Design,” Tech. Rep. NASA/CP-98-208527, Pratt & Whitney.
2.
Meierhofer, B., and Franklin, C. J., 1981, “An Investigation of a Preswirled Cooling Airflow to a Turbine Disc by Measuring the Air Temperature in the Rotating Channels,” ASME Paper 81-GT-132.
3.
El-Oun
,
Z. B.
, and
Owen
,
J. M.
,
1988
, “
,”
ASME J. Turbomach.
,
111
, pp.
522
529
.
4.
Wilson
,
M.
,
Pilbrow
,
R.
, and
Owen
,
J. M.
,
1997
, “
Flow and Heat Transfer in a Pre-Swirl Rotor-Stator System
,”
ASME J. Turbomach.
,
119
, pp.
364
373
.
5.
Dittmann
,
M.
,
Geis
,
T.
,
Schramm
,
V.
,
Kim
,
S.
, and
Wittig
,
S.
,
2002
, “
Discharge Coefficients of a Preswirl System in Secondary Air Systems
,”
ASME J. Turbomach.
,
124
, pp.
119
124
.
6.
Kline
,
S.
, and
McClintock
,
F. A.
,
1953
, “
Describing Uncertainties in Single-Sample Experiments
,”
Mech. Eng. (Am. Soc. Mech. Eng.)
,
75
, pp.
3
8
.
7.
Zimmermann, H., Kutz, J., and Fischer, R., 1998, “Air System Correlations Part 2: Rotating Holes and Two Phase Flow,” ASME Paper 98-GT-207.
8.
Popp
,
O.
,
Zimmermann
,
H.
, and
Kutz
,
J.
,
1998
, “
,”
ASME J. Turbomach.
,
120
, pp.
43
49
.
9.
Geis, T., Rottenkolber, G., Dittmann, M., Richter, B., Dullenkopf, K., and Wittig, S., 2002, “Endoscopic PIV-Measurements in an Enclosed Rotor-Stator System With Pre-Swirled Cooling Air,” 11th International Symposium on Applications of Laser Techniques to Fluid Mechanics, Lisbon, Portugal.
10.
Wittig, S., Kim, S., Scherer, T., Jakoby, R., and Weißert, I., 1995, “Durchfluß an rotierenden Wellen- und Scheibenbohrungen und Wa¨rmeu¨bergang an rotierenden Wellen,” Forschungsvereinigung Verbrennungskraftmaschinen (FVV), Abschlußbericht, Vorhaben Nr. 465 und 536, Heft 574.
11.
McGreehan
,
W. F.
, and
Schotsch
,
M. J.
,
1988
, “
Flow Characteristics of Long Orifices With Rotation and Corner Radiusing
,”
ASME J. Turbomach.
,
110
, pp.
213
217
.