Detached Eddy Simulation of Film Cooling Performance on the Trailing Edge Cutback of Gas Turbine Airfoils

[+] Author and Article Information
P. Martini, A. Schulz, H. -J. Bauer

Lehrstuhl und Institut für Thermische Strömungsmaschinen, Universität Karlsruhe (TH), Kaiserstr. 12, 76128 Karlsruhe, Germany

C. F. Whitney

 ALSTROM Power Technology Centre, Cambridge Road, Whetstone, Leicester LE8 6LH, UK

J. Turbomach 128(2), 292-299 (Feb 01, 2005) (8 pages) doi:10.1115/1.2137739 History: Received October 01, 2004; Revised February 01, 2005

The present study deals with the unsteady flow simulation of trailing edge film cooling on the pressure side cut back of gas turbine airfoils. Before being ejected tangentially on the inclined cut-back surface, the coolant air passes a partly converging passage that is equipped with turbulators such as pin fins and ribs. The film mixing process on the cut back is complicated. In the near slot region, due to the turbulators and the blunt pressure side lip, turbulence is expected to be anisotropic. Furthermore, unsteady flow phenomena like vortex shedding from the pressure side lip might influence the mixing process (i.e., the film cooling effectiveness on the cut-back surface). In the current study, three different internal cooling designs are numerically investigated starting from the steady RaNS solution, and ending with unsteady detached eddy simulations (DES). Blowing ratios M=0.5; 0.8; 1.1 are considered. To obtain both, film cooling effectiveness as well as heat transfer coefficients on the cut-back surface, the simulations are performed using adiabatic and diabatic wall boundary conditions. The DES simulations give a detailed insight into the unsteady film mixing process on the trailing edge cut back, which is indeed influenced by vortex shedding from the pressure side lip. Furthermore, the time averaged DES results show very good agreement with the experimental data in terms of film cooling effectiveness and heat transfer coefficients.

Copyright © 2006 by American Society of Mechanical Engineers
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Figure 1

Cross-sectional view of a turbine blade with pressure side cut back

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Figure 2

Computational domain and internal design of the trailing edge cooling configurations

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Figure 3

Computational grid and types of boundary conditions used for the simulations

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Figure 4

Discharge behavior of trailing edge coolant slots

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Figure 5

Nondimensional temperature distribution and laterally averaged film cooling effectiveness (G1, M=0.80; steady computation)

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Figure 6

DES of G1: instantaneous contours of static temperature and isosurface (T=400K)

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Figure 7

Instantaneous and time-averaged nondimensional temperature distribution for M=0.80 (DES computation)

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Figure 8

FFT spectrum of time variant velocity components (u,v,w) at two monitor points (x∕H=4,y∕H=1.5) for M=0.80

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Figure 9

Distribution of instantaneous and time-averaged film cooling effectiveness for different cooling slots and M=0.80

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Figure 10

Laterally averaged film cooling effectiveness for different blowing ratios M (upper row: G1; middle row: G2a; lower row: G2b)

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Figure 11

Laterally averaged heat transfer coefficient for different blowing ratios M (upper row: G1; middle row: G2a; lower row: G2b)




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