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Numerical Simulation of the Effects of Surface Curvature on the Cooling of Vertically-Injected Jet Layers into a Lateral Turbulent Flow

Shalchi Tabrizi, Amir | 2010

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 40860 (45)
  4. University: Sharif University of Technology
  5. Department: Aerospace Engineering
  6. Advisor(s): Taiebi Rahni, Mohammad; Ramezanizadeh, Mehdi
  7. Abstract:
  8. An improvement of thermal efficiency of modern gas turbines is achieved by increasing turbine inlet temperatures. One of the methods of turbine cooling is to form a film layer on the external surfaces of the blades, so that they can work at high temperatures. Most of the studies concentrate on flat plate geometries with injection through slots or rows of holes. Turbine blade surfaces usually have curvatures which seem to alter the flow field significantly on the film-cooled surfaces. However, there are few reports which investigate the effect of curvature on three-dimensional jet flow injected into the turbulent boundary layer over a curved surface. The surface curvature and the blowing ratio are parameters that affect the film cooling effectiveness. In this work, the adiabatic film cooling effectiveness on convex and concave surfaces (as a model for suction and pressure side film cooling of gas turbine blades) with one row of injection holes are investigated, using numerical simulation and Reynolds average Navier Stokes (RANS) approach. Two different radii of curvature (R/D = 60, 90) with film cooling holes are considered. First, the Navier Stokes equation are transformed to curvilinear coordinates. Then, using finite volume method and SIMPLE algorithm, the curvilinear Navier Stokes equations are discritized. For turbulent modeling, shear stress transport model (SST) is used. The blowing rates are 0.5 and 1.0 and the main stream Reynolds numbers is 10,000. At low and moderate blowing rates the effectiveness is enhanced on convex and reduced on concave surfaces, compared to the results obtained for the flat surface. Also, the adiabatic film effectiveness is higher on the convex surface than on a flat or concave surface at low and moderate blowing rates. However, the effects at high blowing rates seem to be less pronounced. At high blowing rates, the effectiveness is not greatly influenced by surface curvature.
  9. Keywords:
  10. Numerical Simulation ; Shear Stress Transport Turbulance Model ; Curvilinear Coordinates ; Surface Curvature Effect ; Film Cooling ; Gas Turbines ; Reynolds Average Navier-Stocks (RANS)Method

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