This paper investigates the film cooling characteristics and flow structure of trailing edge cutback in turbine vanes,and explains the unsteady flow mixing mechanism of this cooling structure using Proper Orthogonal D...This paper investigates the film cooling characteristics and flow structure of trailing edge cutback in turbine vanes,and explains the unsteady flow mixing mechanism of this cooling structure using Proper Orthogonal Decomposition(POD) method.The Delayed Detached Eddy Simulation(DDES) turbulence model was used to obtain detailed information about the velocity and temperature field for the POD method.To verify the accuracy of the numerical results,fast-response Pressure Sensitive Paint(PSP) and high-frequency Particle Image Velocimetry(PIV) experiments were also conducted,and the results achieved good agreement.As the blowing ratio increases,the effectiveness η of the cutback's film cooling exhibits a "increase-decrease-increase" trend,with η reaching its minimum point at around a blowing ratio(M_(slot)) of 0.75.Three kinds of coherent vortex structures are observed in the flow field at different blowing ratios.According to the analysis using the POD method,the first and second order modes of a Karman-like vortex street are observed in the vicinity of the wall at various blowing ratios.This coherent flow structure is directly related to the mixing intensity between the mainstream gas and the coolant.At M_(slot)=0.75,these modes had the highest energy ratio and formed a stable dominant coherent structure in the flow field.As the blowing ratio increases,the main characteristic modes in the temperature field gradually change,and the mode appears crescent-shaped when the effectiveness of film cooling is at its lowest.This paper combines the vortex structure of the flow field to explain the flow field feature distribution at the lowest effectiveness point η and analyzes its impact on the film cooling characteristics of the protected surface.展开更多
基金financial support of National Natural Science Foundation of China (Grant No.52306055)National Science and Technology Major Project (J2019-Ⅱ-0022-0043)Youth Innovation Promotion Association of the Chinese Academy of Sciences。
文摘This paper investigates the film cooling characteristics and flow structure of trailing edge cutback in turbine vanes,and explains the unsteady flow mixing mechanism of this cooling structure using Proper Orthogonal Decomposition(POD) method.The Delayed Detached Eddy Simulation(DDES) turbulence model was used to obtain detailed information about the velocity and temperature field for the POD method.To verify the accuracy of the numerical results,fast-response Pressure Sensitive Paint(PSP) and high-frequency Particle Image Velocimetry(PIV) experiments were also conducted,and the results achieved good agreement.As the blowing ratio increases,the effectiveness η of the cutback's film cooling exhibits a "increase-decrease-increase" trend,with η reaching its minimum point at around a blowing ratio(M_(slot)) of 0.75.Three kinds of coherent vortex structures are observed in the flow field at different blowing ratios.According to the analysis using the POD method,the first and second order modes of a Karman-like vortex street are observed in the vicinity of the wall at various blowing ratios.This coherent flow structure is directly related to the mixing intensity between the mainstream gas and the coolant.At M_(slot)=0.75,these modes had the highest energy ratio and formed a stable dominant coherent structure in the flow field.As the blowing ratio increases,the main characteristic modes in the temperature field gradually change,and the mode appears crescent-shaped when the effectiveness of film cooling is at its lowest.This paper combines the vortex structure of the flow field to explain the flow field feature distribution at the lowest effectiveness point η and analyzes its impact on the film cooling characteristics of the protected surface.
