Abstract

This paper presents two-dimensional LDA measurements of the convection of a wake through a low-pressure turbine cascade. Previous studies have shown the wake convection to be kinematic, but have not provided details of the turbulent field. The spatial resolution of these measurements has facilitated the calculation of the production of turbulent kinetic energy, and this has revealed a mechanism for turbulence production as the wake convects through the blade row. The measured ensemble-averaged velocity field confirmed the previously reported kinematics of wake convection while the measurements of the turbulence quantities showed the wake fluid to be characterized by elevated levels of turbulent kinetic energy (TKE) and to have an anisotropic structure. Based on the measured mean and turbulence quantities, the production of turbulent kinetic energy was calculated. This highlighted a TKE production mechanism that resulted in increased levels of turbulence over the rear suction surface where boundary-layer transition occurs. The turbulence production mechanism within the blade row was also observed to produce more anisotropic turbulence. Production occurs when the principal stresses within the wake are aligned with the mean strains. This coincides with the maximum distortion of the wake within the blade passage and provides a mechanism for the production of turbulence outside of the boundary layer.

Issue Section:
Technical Papers
Keywords:
wakes, confined flow, boundary layer turbulence, convection, flow measurement, turbines, flow instability, laser Doppler anemometry, laminar to turbulent transitions
Topics:
Blades, Cascades (Fluid dynamics), Convection, Pressure, Turbines, Turbulence, Wakes, Stress, Wake turbulence, Fluids, Flow (Dynamics), Anisotropy, Kinematics, Kinetic energy, Turbine blades
1.
Hodson, HP, 1998, “Bladerow Interactions In Low Pressure Turbines,” Blade Row Interference Effects Axial Turbomachinery Stages, Von Karman Institute, Brussels, Belgium, in VKI Lecture Series No. 1998-02, Feb 9.
2.
Howell, R. J., Hodson, H. P., Schulte, V., Schiffer, H-P., Haselbach, F., and Harvey, N. W., 2001, “Boundary Layer Development on the BR710 and BR715 LP Turbines-The Implementation of High Lift and Ultra High Lift Concepts,” ASME Paper No. 2001-GT-0441.
3.
Cobley, K., Coleman, N., Siden, G., and Arndt, N., 1997, “Design of New Three Stage Low Pressure Turbine for BMW Rolls-Royce BR715 Engine,” ASME Paper No. 97-GT-419.
4.
Meyer
,
R. X.
,
1958
, “
The Effects of Wakes on the Transient Pressure and Velocity Distributions in Turbomachines
,”
ASME J. Basic Eng.
,
80
, pp.
1544
–
1552
.
5.
Hodson
,
H. P.
,
1985
, “
A Blade-to-Blade Prediction of Wake-Generated Unsteady Flow
,”
ASME J. Eng. Gas Turbines Power
,
107
.
6.
Giles, M. B., 1987, “Calculation of Unsteady Wake/Rotor Interactions,” AIAA 25th Aerospace Sciences Meeting, Reno, AIAA Paper 87-0006.
7.
Addison
,
J. S.
, and
Hodson
,
H. P.
,
1992
, “
Modelling of Unsteady Transitional Boundary Layers
,”
ASME J. Turbomach.
,
114
(
3
), pp.
580
–
589
.
8.
Doorly, D. L., and Oldfield, 1985, “Simulation of the Effects of Shock Wave Passing on a Turbine Rotor Blade,” ASME Paper No. 85-GT-112.
9.
La Graff
,
J. E.
,
Ashworth
,
D. A.
, and
Schultz
,
D. L.
,
1989
, “
Measurements and Modelling of the Gas Turbine Blade Transition Process as Disturbed by Wakes
,”
ASME J. Turbomach.
,
111
, pp.
315
–
322
.
10.
Stieger, R. D., and Hodson, H. P., 2003, “The Transition Mechanism of Highly Loaded LP Turbine Blades,” ASME Paper No. GT2003-38304.
11.
Stieger, R. D., Hollis, D., and Hodson, H. P., 2003, “Unsteady Surface Pressures Due to Wake Induced Transition in a Laminar Separation Bubble on a LP Turbine Cascade,” ASME Paper No. GT2003-38303.
12.
Schulte, V., 1995, “Unsteady Separated Boundary Layers in Axial-flow Turbomachinery,” Ph.D. dissertation, Cambridge Univ., Cambridge, England.
13.
Halstead, D. E., 1997, “Flowfield unsteadiness and turbulence in multistage low pressure turbines,” Conf. Boundary layer transition in turbomachines, Syracuse Univ., Minnowbrook, Sep 7–10.
14.
George, W. K., 1975, “Limitations to Measuring Accuracy Inherent in the Laser-Doppler Signal,” Proc. LDA Symp., Copenhagen.
Copyright © 2005
 by ASME
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