The paper experimentally studies the effects of periodic unsteady wake flow on boundary layer development, separation and reattachment along the suction surface of a low pressure turbine blade. The experimental investigations were performed on a large scale, subsonic unsteady turbine cascade research facility at the Turbomachinery Performance and Flow Research Laboratory (TPFL), Texas A&M University. The experiments were carried out at a Reynolds number of 110,000 (based on suction surface length and exit velocity) with a free-stream turbulence intensity of 1.9%. One steady and two different unsteady inlet flow conditions with the corresponding passing frequencies, wake velocities, and turbulence intensities were investigated. The reduced frequencies cover the entire operating range of LP turbines. In addition to the unsteady boundary layer measurements, blade surface measurements were performed at the same Reynolds number. The surface pressure measurements were also carried out at one steady and two periodic unsteady inlet flow conditions. The results presented in ensemble-averaged, and the contour plot forms help to understand the physics of the separation phenomenon under periodic unsteady wake flow. It was found that the suction surface displayed a strong separation bubble for these three different reduced frequencies. For each condition, the locations and the heights defining the separation bubble were determined by carefully analyzing and examining the pressure and the mean velocity profile data. The location of boundary layer separation was independent of the reduced frequency level. However, the extent of the separation was strongly dependent on the reduced frequency level. Once the unsteady wake started to penetrate into the separation bubble, the turbulent spot produced in the wake paths caused a reduction of the separation bubble height.

Issue Section:
Technical Papers
Keywords:
wakes, boundary layer turbulence, flow separation, turbines, subsonic flow, bubbles, confined flow, flow simulation
Topics:
Blades, Boundary layers, Bubbles, Pressure, Separation (Technology), Suction, Wakes, Turbulence, Flow (Dynamics), Turbines, Cascades (Fluid dynamics), Turbine blades
1.
Pfeil, H., and Herbst R., 1979, “Transition Procedure of Instationary Boundary Layers,” ASME Paper No. 79_GT_128.
2.
Pfeil
,
H.
,
Herbst
,
R.
, and
Schro¨der
,
T.
,
1983
, “
Investigation of the Laminar Turbulent Transition of Boundary Layers Disturbed by Wakes
,”
ASME J. Eng. Power
,
105
, pp.
130
–
137
.
3.
Orth
,
U.
,
1993
, “
Unsteady Boundary Layer Transition in Flow Periodically Disturbed by Wakes
,”
ASME J. Turbomach.
,
115
, pp.
707
–
713
.
4.
Schobeiri, M. T., and Radke, R. E., 1994, “Effects of Periodic Unsteady Wake Flow and Pressure Gradient on Boundary Layer Transition Along the Concave Surface of a Curved Plate,” ASME Paper 94-GT-327, presented at the International Gas Turbine and Aero-Engine Congress and Exposition, The Hague, Netherlands, June 13–16, 1994.
5.
Schobeiri
,
M. T.
,
Read
,
K.
, and
Lewalle
,
J.
,
2003
, “
Effect of Unsteady Wake Passing Frequency on Boundary Layer Transition, Experimental Investigation and Wavelet Analysis
,”
ASME J. Fluids Eng.
,
125
, pp.
251
–
266
.
6.
Wright
,
L.
, and
Schobeiri
,
M. T.
,
1999
, “
The Effect of Periodic Unsteady Flow on Boundary Layer and Heat Transfer on a Curved Surface
,”
ASME Trans. J. Heat Transfer
,
120
, pp.
22
–
33
.
7.
Chakka
,
P.
, and
Schobeiri
,
M. T.
,
1999
, “
Modeling of Unsteady Boundary Layer Transition on a Curved Plate Under Periodic Unsteady Flow Condition: Aerodynamic and Heat Transfer Investigations
,”
ASME Trans. J. Turbomach.
,
121
, pp.
88
–
97
.
8.
Liu
,
X.
, and
Rodi
,
W.
,
1991
, “
Experiments on Transitional Boundary Layers With Wake-Induced Unsteadiness
,”
J. Fluid Mech.
,
231
, pp.
229
–
256
.
9.
Schobeiri, M. T., Pappu, K., and Wright, L., 1995, “Experimental Sturdy of the Unsteady Boundary Layer Behavior on a Turbine Cascade,” ASME 95-GT-435, presented at the International Gas Turbine and Aero-Engine Congress and Exposition, Houston, Texas, June 5–8, 1995.
10.
Schobeiri
,
M. T.
,
John
,
J.
, and
Pappu
,
K.
,
1997
, “
Experimental Study on the Effect of Unsteadiness on Boundary Layer Development on a Linear Turbine Cascade
,”
J. Exp. Fluids
,
23
, pp.
303
–
316
.
11.
Schobeiri
,
M. T.
, and
Wright
,
L.
,
2003
, “
Advances in Unsteady Boundary Layer Transition Research
,”
Int. J. Rotating Mach.
,
9
(
1
), pp.
1
–
22
.
12.
Schobeiri
,
M. T.
, and
Chakka
,
P.
,
2002
, “
Prediction of Turbine Blade Heat Transfer and Aerodynamics Using Unsteady Boundary Layer Transition Model
,”
Int. J. Heat Mass Transfer
,
45
, pp.
815
–
829
.
13.
Brunner, S., Fottner, L., and Schiffer, H.-P., 2000, “Comparison of Two Highly Loaded Turbine Cascade Under the Influence of Wake-Induced Transition,” ASME 2000-GT-268, presented at the International Gas Turbine and Aero-Engine Congress and Exposition, Munich, Germany, May 8–11, 2000.
14.
Cardamone, P., Stadtmu¨ller P., Fottner, L., and Schiffer, H.-P., 2000, “Numerical Investigation of the Wake-Boundary Layer Interaction on a Highly Loaded LP Turbine Cascade Blade,” ASME 2002-GT-30367, presented at the International Gas Turbine and Aero-Engine Congress and Exposition, Amsterdam, Netherlands, June 3–6, 2002.
15.
Schulte, V., and Hodson, H. P., 1996, “Unsteady Wake-Induced Boundary Layer Transition in High Lift LP Turbines,” ASME Paper No. 96-GT-486.
16.
Kaszeta, R., Simon T. W., and Ashpis, D. E., 2001, “Experimental Investigation of Transition to Turbulence as Affected by Passing Wakes,” ASME Paper 2001-GT-0195.
17.
Lou, W., and Hourmouziadis, J., 2000, “Separation Bubbles Under Steady and Periodic Unsteady Main Flow Conditions,” ASME Paper 200-GT-270.
18.
Volino
,
R. J.
, and
Hultgren
,
L. S.
,
2001
, “
Measurements in Separated and Transitional Boundary Layers Under Low-Pressure Turbine Airfoil Conditions
,”
ASME J. Turbomach.
,
123
, pp.
189
–
197
.
19.
Schro¨der, Th., 1989, “Measurements With Hot-Film Probes and Surface Mounted Hot Film Gages in a Multi-Stage Low Pressure Turbine,” European Propulsion Forum, Bath, UK.
20.
Haueisen V., Hennecke D. K., and Schro¨der, T., 1997, “Measurements With Surface Mounted Hot Film Sensors on Boundary Layer Transition in Wake Disturbed Flow,” AGARD-CP-598.
21.
Shyne
,
R. J.
,
Sohn
,
K. H.
, and
De Witt
,
K. J.
,
2000
, “
Experimental Investigation of Boundary Layer Behavior in a Simulated Low Pressure Turbine
,”
ASME J. Fluids Eng.
,
122
, pp.
84
–
89
.
22.
Treuren
,
K. W. V.
,
Simon
,
T.
,
Koller
,
M. V.
,
Byerley
,
A. R.
,
Baughn
,
J. W.
, and
Rivir
,
R.
,
2002
, “
Measurements in a Turbine Cascade Flow Under Ultra Low Reynolds Number Conditions
,”
ASME J. Turbomach.
,
124
, pp.
100
–
106
.
23.
Halstead
,
D. E.
,
Wisler
,
D. C.
,
Okiishi
,
T. H.
,
Walker
,
G. J.
,
Hodson
,
H. P.
, and
Shin
,
H.-W.
,
1997
, “
Boundary Layer Development in Axial Compressors and Turbines: Part 3 of 4
,”
ASME J. Turbomach.
,
119
, pp.
225
–
237
.
24.
Schobeiri, M. T., and Oztu¨rk, B., 2003, “On the Physics of the Flow Separation Along a Low Pressure Turbine Blade Under Unsteady Flow Conditions,” ASME 2003-GT-38917, presented at International Gas Turbine and Aero-Engine Congress and Exposition, Atlanta, Georgia, June 16–19, 2003.
25.
Schobeiri
,
M. T.
,
John
,
J.
, and
Pappu
,
K.
,
1996
, “
Development of Two-Dimensional Wakes Within Curved Channels, Theoretical Framework and Experimental Investigation
,”
ASME Trans. J. Turbomach.
,
118
, pp.
506
–
518
.
26.
Schobeiri
,
M. T.
,
2001
, “
Experimental Determination of LPT-Profile Losses at Low Reynolds Numbers
,”
Progress Report No
12, October 25, 2001, NASA GRC, Project Monitor: Dr. D. Ashpis.
27.
Hourmouziadis, J., 1989, “Blading Design for Axial Turbomachines,” AGARD, Lecture Series LS-167.
28.
Eifler, J., 1975, “Zur Frage der freien turbulenten Stro¨mungen, insbesondere hinter ruhenden und bewegten Zylindern,” Dissertation D-17, Technische Hochschule Darmstadt, Germany.
29.
Kline
,
S. J.
, and
McKlintock
,
F. A.
,
1953
, “
Describing Uncertainties in Single-Sample Experiments
,”
Mech. Eng. (Am. Soc. Mech. Eng.)
,
75
, pp.
3
–
8
.
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