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Computational Thermal Sciences: An International Journal
ESCI SJR: 0.249 SNIP: 0.434 CiteScore™: 0.7

ISSN Print: 1940-2503
ISSN Online: 1940-2554

Computational Thermal Sciences: An International Journal

DOI: 10.1615/ComputThermalScien.2017020468
pages 151-165

NUMERICAL INVESTIGATION OF FILM-COOLING EFFECTIVENESS DOWNSTREAM OF A MICRO RAMP

Hamza Khamane
Laboratory of Naval Aero-Hydrodynamic, Faculty of Mechanical Engineering, Oran University of Sciences and Technology, PO Box 1505, El-Mnaouar Oran, Algeria
Abbes Azzi
Laboratory of Naval Aero-Hydrodynamic, Faculty of Mechanical Engineering, Oran University of Sciences and Technology, PO Box 1505, El-Mnaouar Oran, Algeria
Zakaria Mansouri
Institut de Combustion Aérothermique Réactivité et Environnement, CNRS 1 C Avenue de la Recherche Scientifique, 45071 Orléans Cedex 2, France

ABSTRACT

Gas turbine blades operate under high temperatures and thermal stresses caused by hot combustion gases issuing from the combustion chamber. A film-cooling technique is usually used to protect the surfaces of the blades and to avoid turbine damage. This paper investigates numerically the effect of a micro ramp (MR) on film-cooling performance in a jet-crossflow configuration. The configuration comprises an inclined coolant jet at 35° interacting with a hot crossflow. The micro ramp is placed downstream of the jet, where different heights of MR are investigated. The numerical simulations are carried out using Reynolds-averaged Navier-Stokes (RANS) technique with realizable k-ε as a turbulence closure model. Validations of the computational model with the experimental data are performed, and good agreement is found. The flow field and vortices downstream of the jet are analyzed for baseline and MR configurations. Results reported that the counter-rotating vortex pair (CRVP) is present for the baseline configuration and is not found inMR configurations. In addition, the flow field shows significant changes at each height of MR. Furthermore, the film-cooling effectiveness is analyzed and discussed according to the thickness, width, and inclination angle of the thermal layer (coolant jet) on the flat plate. It is found that the highest MR used is the most reliable and it enhances significantly the film-cooling effectiveness compared with the other MR configurations. Finally, the effect of two blowing ratios (M = 1 and M = 1.5) on film-cooling effectiveness is investigated. Results indicated that the maximum effectiveness is found at M = 1.5 with the highest MR (Ramp C).


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