Evaluation of mist/air film cooling of C3X vane with serrate-type trenched holes

Abstract

• Film cooling of C3X vane with serrate-type trenched holes using mist/air mixture under practical conditions is evaluated. • Both serrated transverse trench structure and addition of mist to air can significantly improve film cooling performance. • Replacing the trench edge by a double-curvature lip structure can further improve the film cooling effectiveness. • Film cooling effectiveness of the vane is reduced when the angle of the serrated trench is too large. • Vortex for the six trenched holes intensifies with the increase in the mass flow rate . Serrate-type trenched cooling holes have shown good film cooling performance for the cooling of turbine vanes using coolant air. Mist-assisted film cooling has also exhibited great potential for efficient cooling of a turbine vane. The combination of them may create a substantial improvement of cooling performance, which is explored in this simulation. This work studies the influence of serrate structure on the cooling performance of trenched holes for the C3X turbine vane under practical conditions by examining the flow and heat transfer characteristics of the mist/air mixture. The results prove the concept proposed for significantly improving the cooling performance. At the mass flow ratio R c = 0.25% ( M = 0.5) and R c = 0.50% ( M = 1.0), replacing the trench edge by a double-curvature lip structure can further improve the film cooling effectiveness. The film cooling effectiveness of the vane is reduced when the angle of the serrated trench is too large and the vortex for the six trenched holes intensifies with increasing mass flow ratio. The comparison of streamlines distribution and vortex structures at different blowing ratios by the Q criterion for the trenched holes in the flat plate reveals why the serrated trench structure can improve the cooling effectiveness: it can generate anti-counter-rotating vortices, making it difficult for the coolant film to separate from the wall. Although it is worth of further study on this novel design of serrated trench with mist/air film cooling under engine-representative conditions, this work provide heuristic guidance for the cooling of turbine vanes.