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ISBN 9783843929240

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978-3-8439-2924-0, Reihe Thermodynamik

Kristian Haase
Experimental investigation of the Ice Formation Method applied to the endwall of a turbine stator vane row

215 Seiten, Dissertation Universität Stuttgart (2016), Softcover, A5

Zusammenfassung / Abstract

The constantly increasing scarcity of fossil fuels requires engineers to further improve efficiencies of combustion engines in order to use the still available resources as efficiently as possible. This can be achieved by further increasing the combustion temperature, which however results in the necessity of additional cooling for highly stressed components, e.g. turbine vane endwalls. In turn, the increased extraction of cooling air from the compressor negatively affects the overall efficiency.

An approach to overcome this negative effect is the endwall contouring, which is well-known to turbine designers for its ability to reduce heat transfer from the hot combustion gas into the components. In the present study, the Ice Formation Method (IFM) is experimentally applied to the endwall of a generic turbine vane row in order to three-dimensionally shape its surface and reduce and homogenise heat load. In steady state, the ice layers always feature a minimum entropy production rate, which is the natural goal function of the optimisation process.

The experiments are conducted in a water channel test facility, in which the linear three passage cascade with its cooled endwall is implemented. Multiple configurations with cooled vanes, short and extended cooled endwalls, upstream slit injection and lowered cooled endwall are investigated using the IFM. All ice layers have in common that heat transfer maxima occur around the vane leading edges, due to impinging flow of the horseshoe vortices, and also near the passage exit cross section. Furthermore, the ice layers exhibit different peculiarities that generally occur for all experiments with the different configurations. These are e.g. fillets in the vane-endwall juncture for the cooled vane experiments or an exceptionally low ice thickness in the inlet channel with slit injection. These characteristics result in considerably different heat transfer distributions and confirm the adaptability of the IFM to various geometric variations.

The present study shows that the Ice Formation Method can be applied successfully to the complex geometry of a turbine vane row in order to generate novel, three-dimensionally shaped surfaces. Experimental assessment of the heat transfer performance is difficult but numerical investigations confirm that the ice layers are optimised to a minimum entropy production rate and simultaneously also show high potential in reducing endwall heat load compared to the flat endwall.