Numerical optimization of triangular concave edge shaped ramp in film cooling

Abstract

 Film cooling effectiveness enhances with decreasing ramp angle  Film cooling effectiveness enhances with increasing ramp height  Ramp increases lateral spreading of the coolant stream Figure A. Detailed view of the physical model, a) section view, b) location of the ramp on the surface, c) numerical simulation region Purpose: Purpose of this study is to investigate the optimum design parameter of the triangular concave edge shaped upstream ramp under different flow condition for film cooling effectiveness. Theory and Methods: Numerical simulations were conducted using Ansys FLUENT. Performance of most widely used RANS model were compared and Transition k-kl-ω was used. Numerical solution procedure was validated with available experimental data in the literature. Area-averaged film cooling effectiveness (FCE), laterally-averaged FCE, longitudinally-averaged FCE and local FCE were quantitatively investigated comprehensively. In order to reveal the underlying physics of the influence of ramp on FCE, the vortices emerged in the flow field and the velocity profile of the flow were also examined. Results:Results showed that lateral spreading of the coolant were increased by locating ramp on the surface. Areaaveraged FCE is enhanced 305.44% with h/d=0.50 and αr=10˚ compared to conventional film cooling configuration. While highest area-averaged FCE achieved at relatively low blowing ratio (M=0.60) for conventional film cooling, increasing blowing ratio also increases area-averaged FCE by mounting upstream ramp on the surface. Conclusion:Counter rotating vortex (CRV) on the coolant flow detaches the coolant from the surface. Ramp creates anti-CRV on the coolant flow and prevents the coolant separation. Strength of anti-CRV on jet flow increases with decreasing ramp angle and increasing ramp height, therefore FCE increases with decreasing ramp angle and increasing ramp height. Furthermore, most feasible design parameters of ramp for film cooling effectiveness are h/d=0.50 and αr=10˚