Experimental results are presented which show the influence on the secondary flow and its losses by a profile modification of the leading edge very close to the endwall. The investigation was carried out with a well-known turbine profile that originally was developed for highly loaded low pressure turbines. The tests were done in a low speed cascade wind tunnel. The geometrical modification was achieved by a local thickness increase; a leading edge endwall bulb. It was expected that this would intensify the suction side branch of the horse-shoe (hs-) vortex with a desirable weakening effect on the passage vortex. The investigated configuration shows a reduction of secondary losses by 2.1 percent points that represents approximately 50 percent of these losses compared to the reference profile. Detailed measurements of the total pressure field behind the cascade are presented for both the reference and the modified profile. The influence of the modified hs-vortex on the overall passage vortex can be clearly seen. The results of a numerical analysis are compared with the experimental findings. A numerical analysis shows that the important details of the experimental findings can be reproduced. Quantitative values are locally different. The theoretical approach taken cannot yet be used for an exact prediction of the loss reduction. However, the analysis of the interaction and the resulting tendencies are considered to be valid. Hence, theoretical investigations as a guideline for the design of a leading edge bulb at the endwall are a valuable tool.

Issue Section:
Technical Papers
Keywords:
gas turbines, losses, wind tunnels, vortices, pressure measurement, numerical analysis, boundary layers
Topics:
Boundary layers, Cascades (Fluid dynamics), Flow (Dynamics), Numerical analysis, Pressure, Turbines, Vortices, Suction, Wind tunnels, Blades, Design
1.
Sauer, H., and Wolf, H., 1997, “Influencing the Secondary Flow in Turbine Cascades by the Modification of the Blade Leading Edge,” 2, European Conference on Turbomachinery, Antwerpen.
2.
NUMECA International, 1997, “Manual FINE/TURBO™, IGG, Euranus, CFView,” Brussels.
3.
Sauer, H., and Wolf, H., 1993, “The Influence of the Inlet Boundary Layers on the Secondary Losses of Turbine Stages,” AGARD-Conference Proceedings, 537, Montreal, Canada, Oct.
4.
Ro¨mer, N., 1990, “Untersuchungen zum Umschlagverhalten der Profilgrenzschicht an Verdichter- und Turbinengittern,” Dissertation Univ. d. Bundeswehr Mu¨nchen.
5.
Weiβ, P. A., 1993, “Der Einfluss der Profilgeometrie auf die Entwicklung der Sekunda¨rstro¨mungen in Turbinengittern,” Dissertation Univ. d. Bundeswehr Mu¨nchen.
6.
Raab, I., Duden, A., and Fottner, L., 1998, “Controlling the Secondary Flow in a Turbine Cascade by 3D Airfoil Design and Endwall Contouring,” ASME Paper No. 98-GT-72.
7.
Hildebrandt, T., 1997, Weiterentwicklung von 3D Navier-Stokes-Stro¨mungsrechenverfahran zur Anwendung in hochbelasteten Verdichter- und Turbinengittern, Dissertation Univ. d. Bundeswehr Mu¨nchen.
8.
Mobarak, A., 1989, “Study of Various Factors Affecting Secondary Loss Vortices Downstream a Straight Turbine Cascade,” ASME Paper No. 89-GT-12.
9.
Gotthardt, H., 1983, “Theoretische und experimentelle Untersuchungen an ebenen Turbinengittern mit Pfeilung und V-Stellung,” Dissertation TU Braunschweig.
Copyright © 2001
 by ASME
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