This paper examines the effect of aerofoil surface film cooling on the aerodynamic efficiency of an annular cascade of transonic nozzle guide vanes. A dense foreign gas (SF6/Ar mixture) is used to simulate engine representative coolant-to-mainstream density ratios under ambient conditions. The flowfield measurements have been obtained using a four-hole pyramid probe in a short duration blowdown facility that correctly models engine Reynolds and Mach numbers, as well as the inlet turbulence intensity. The use of foreign gas coolant poses specific challenges not present in an air-cooled cascade, and this paper addresses two. First, a novel method for the determination of mass flow from pneumatic probe data in a heterogeneous gas environment is presented that eliminates the need to measure concentration in order to determine loss. Second, the authors argue on the grounds of dimensionless similarity that momentum flux ratio is to be preferred to blowing rate for the correct parameterization of film cooling studies with varying coolant densities. Experimental results are presented as area traverse maps, from which values for loss have been calculated. It is shown that air and foreign gas at the same momentum flux ratio give very similar results, and that the main difference between cooled and uncooled configurations is an increase in wake width. Interestingly, it is shown that an increase in the momentum flux ratio above the design value with foreign gas coolant reduces the overall loss compared with the design value. The data have been obtained both for purposes of design and for CFD code Validation.

1.
Amecke
J.
,
1970
, “
Anwendung der transsonischen Ahnlichkeitsregel auf die Stromung durch ebene Schaufelgitter
,”
VDI Forschungsheft
, Vol.
540
, pp.
16
28
.
2.
Denton
J. D.
,
1993
, “
Loss Mechanisms in Turbomachines
,”
ASME JOURNAL OF TURBOMACHINERY
, Vol.
115
, pp.
621
656
.
3.
Dominy, R. G., and Harding, S. C., 1989, “An investigation of secondary flows in nozzle guide vanes,” AGARD CP-469.
4.
Dzung
L. S.
,
1971
, “
Konsistente Mittelwerte in der Theorie der Turbomaschinen fu¨r Kompressible Medien
,”
BBC-Mitt.
, Vol.
58
, pp.
485
492
.
5.
Haller
B. R.
, and
Camus
J. J.
,
1984
, “
Aerodynamic loss penalty produced by film cooling transonic turbine blades
,”
ASME Journal of Engineering for Gas Turbines and Power
, Vol.
106
, pp.
198
205
.
6.
King, P. I., 1986, “Aerodynamics of high performance turbine blading,” D. Phil. Thesis, University of Oxford.
7.
Kollen, O., and Koschel, W., 1985, “Effect of film-cooling on the aerodynamic performance of a turbine cascade,” AGARD CP-390.
8.
Main
A. J.
,
Day
C. R. B.
,
Lock
G. D.
, and
Oldfield
M. L. G.
,
1996
, “
Calibration of a four-hole pyramid probe and area traverse measurements in a short-duration transonic turbine cascade tunnel
,”
Experiments in Fluids
, Vol.
21
, pp.
302
311
.
9.
Main
A. J.
,
Oldfield
M. L. G.
,
Lock
G. D.
, and
Jones
T. V.
,
1997
, “
Free Vortex Theory for Efficiency Calculations From Annular Cascade Data
,”
ASME JOURNAL OF TURBOMACHINERY
, Vol.
119
, pp.
247
255
.
10.
Martinez-Botas, R. F., Main, A. J., Lock, G. D., and Jones, T. V., 1993, “A cold heat transfer tunnel for gas turbine research on an annular cascade,” ASME Paper No. 93-GT-248.
11.
Mee, D. J., 1992, “Techniques for Aerodynamic Loss Measurement of Transonic Turbine Cascades With Trailing-Edge Region Coolant Ejection,” ASME Paper No. 92-GT-157.
12.
Sieverding, C. H., Van Hove, W., and Boletis, E., 1984, “Experimental study of the three-dimensional flow field in an annular turbine nozzle guide vane,” ASME Journal of Engineering for Gas Turbines and Power, Vol. 106, No. 2.
13.
Teekaram
A. J. H.
,
Forth
C. J. P.
, and
Jones
T. V.
,
1989
, “
The use of foreign gas to simulate the effects of density ratios in film cooling
,”
ASME JOURNAL OF TURBOMACHINERY
, Vol.
111
, pp.
57
62
.
This content is only available via PDF.
You do not currently have access to this content.