This paper describes a program of work, largely experimental, which was undertaken with the objective of developing an improved blade profile for the low-pressure turbine in aero-engine applications. Preliminary experiments were conducted using a novel technique. An existing cascade of datum blades was modified to enable the pressure distribution on the suction surface of one of the blades to be altered. Various means, such as shaped inserts, an adjustable flap at the trailing edge, and changing stagger were employed to change the geometry of the passage. These experiments provided boundary layer and lift data for a wide range of suction surface pressure distributions. The data were then used as a guide for the development of new blade profiles. The new blade profiles were then investigated in a low-speed cascade that included a set of moving bars upstream of the cascade of blades to simulate the effect of the incoming wakes from the previous blade row in a multistage turbine environment. Results are presented for two improved profiles that are compared with a datum representative of current practice. The experimental results include loss measurements by wake traverse, surface pressure distributions, and boundary layer measurements. The cascades were operated over a Reynolds number range from 0.7 × 105 to 4.0 × 105. The first profile is a “laminar flow” design that was intended to improve the efficiency at the same loading as the datum. The other is a more highly loaded blade profile intended to permit a reduction in blade numbers. The more highly loaded profile is the most promising candidate for inclusion in future designs. It enables blade numbers to be reduced by 20 percent, without incurring any efficiency penalty. The results also indicate that unsteady effects must be taken into consideration when selecting a blade profile for the low-pressure turbine.

1.
Banieghbal, M. R., Curtis, E. M., Denton, J. D., Hodson, H. P., Huntsman, I., and Schulte, V. S., 1995, “Wake Passing in LP Turbines,” Paper No. 23, AGARD Conf. Loss Mechanisms and Unsteady Flows in Turbomachines, Derby, May.
2.
Denton
J. D.
,
1993
, “
Loss Mechanisms in Turbomachines
,”
ASME JOURNAL OF TURBOMACHINERY
, Vol.
115
, pp.
621
656
.
3.
Halstead
D. E.
,
Wisler
D. C.
,
Okiishi
T. H.
,
Walker
G. J.
,
Hodson
H. P.
, and
Shin
H.-W.
,
1997
a, “
Boundary Layer Development in Axial Compressors and Turbines: Part 1 of 4—Composite Picture
,”
ASME JOURNAL OF TURBOMACHINERY
, Vol.
119
, pp.
114
127
.
4.
Halstead
D. E.
,
Wisler
D. C.
,
Okiishi
T. H.
,
Walker
G. J.
,
Hodson
H. P.
, and
Shin
H.-W.
,
1997
b, “
Boundary Layer Development in Axial Compressors and Turbines: Part 3 of 4—Turbines
,”
ASME JOURNAL OF TURBOMACHINERY
, Vol.
119
, pp.
232
244
.
5.
Hashimoto, K., and Kimura, T., 1984, “Preliminary Study of Forward Loaded Cascades Designed With Inverse Method for Low Pressure Turbine,” ASME Paper No. 84-GT-65.
6.
Hodson, H. P., Banieghbal, M. R., and Dailey, G. M., 1993, “The Analysis and Prediction of the Effects of Bladerow Interactions in Axial Flow Turbines,” presented at the I Mech. E Conf., Turbomachinery, London, Oct. 1994.
7.
Hodson
H. P.
,
Huntsman
I.
, and
Steele
A. B.
,
1994
, “
An Investigation of Boundary Layer Development in a Multistage LP Turbine
,”
ASME JOURNAL OF TURBOMACHINERY
, Vol.
116
, pp.
375
383
.
8.
Hoheisel
H.
,
Kiock
R.
,
Lichtfuss
H. J.
, and
Fottner
L.
,
1987
, “
Influence of Free-Stream Turbulence and Blade Pressure Gradient on Boundary Layer and Loss Behavior of Turbine Cascades
,”
ASME JOURNAL OF TURBOMACHINERY
, Vol.
109
, pp.
210
219
.
9.
Hourmouziadis, J., 1989, “Aerodynamic Design of Low Pressure Turbines,” AGARD Lecture Series LS-167, June.
10.
Ladwig, M., and Fottner, L., 1993, “Experimental Investigations of the Influence of Incoming Wakes on the Losses of a Linear Turbine Cascade,” ASME Paper No. 93-GT-394.
11.
Lieblein, S., 1956, “Experimental Flow in 2D Cascades,” Chap. VI of The Aerodynamic Design of the Axial Flow Compressor, NACA RME 56B03, reprinted as NASA SP36, 1965.
12.
Schulte, V., and Hodson, H. P., 1994, “Wake-Separation Bubble Interaction in Low Pressure Turbines,” Paper No. AIAA-94-2931.
13.
Schulte, V., and Hodson, H. P., 1996, “Unsteady Wake-Induced Boundary Layer Transition in Highly Loaded LP Turbines,” ASME Paper No. 96-GT-486; accepted for publication in the ASME JOURNAL OF TURBOMACHINERY.
14.
Sutton, A. J., 1990, “The Trailing Edge Loss of Subsonic Turbine Blades,” Msc Thesis, Univ. Cambridge.
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