Ralf Schiele

Gas Turbine Heat Transfer: Past and Future Challenges

The demand for gas turbines with increasing power and efe ciency calls for extremely high temperatures in the hot-gas sections of the engines. These temperatures can only be realized by employing sophisticated cooling schemes. Inadequate cooling may result in excessive material temperatures with reduced reliability and a lifetime of those parts subjected to the hot gas. Based on a survey of the different cooling techniques employed in modern gasturbineenginesandtheirapplicationin gasturbinecombustors, aswellasturbinecomponents,modernaspects and future developments are discussed. Results from laboratory experiments that help to understand the physical phenomena arepresented, as well as theoretical analyses. Thepossibleuse of ceramicmaterialsisdemonstrated by means of tests carried out at the Institut f ¨ ur Thermische Str ¨ omungsmaschinen, University of Karlsruhe. Besides describing current techniques, new developments are assessed and goals for future research are discussed.

Calculating Turbulent and Transitional Boundary-Layers with Two-Layer Models of Turbulence

Publisher Summary A two-layer model of turbulence combining a two-equation model in the fully turbulent region with a one-equation turbulence model near the wall is used to calculate turbulent and transitional boundary-layers. By simulating turbulent boundary-layers the validity of the model and the correct coupling of the two layers are reviewed. A new intermittency function is introduced into the one-equation model enabling the application of the so called TRANSIC - T model (TRANSitional I ntermittency C ontrolled T wo-Layer’ model) to transitional boundary-layers. The model is verified against transitional boundary-layer flows under varying conditions. Its performance is discussed by comparison to experimental data, a revised version of the two-layer model by Fujisawa et al. [1] and four low-Reynolds number k-e turbulence models capable of simulating transitional flows reasonably well.