Influence of streamwise position of crescent-shaped block on flat-plate film cooling characteristics

Abstract

Film cooling injection from discrete circular holes is widely used in gas turbines to reduce the heat load of the turbine blades. Placing a special designed structure upstream or downstream, the circular hole has been proven to be a new effective way to improve cooling effectiveness in recent years. In the present study, numerical investigations were performed on a row of circular holes over a flat plate with crescent-shaped blocks. Totally seven configurations without block, with blocks located at six streamwise positions including 6 times, 5 times, 4 times of hole diameter upstream, and 0.5 times, 1.5 times, 2.5 times of hole diameter downstream at blowing ratios of 0.5-1.5 were tested symmetrically. The Reynolds-averaged Navier-Stokes equations with the k-ω shear-stress transport model were solved. Flow fields, cooling effectiveness and aerodynamic losses were analyzed in detail. Although with different generation mechanism, additional vortex pair opposite to the counter-rotating vortex pair was generated by placing either an upstream or downstream block, which could finally improve the coolant lateral coverage and thus cooling effectiveness. The cooling performances and aerodynamic losses between configurations without block and with blocks at six streamwise positions were then compared. Finally, the optimal streamwise position of the block was recommended at various blowing ratios.

Film Cooling Performance of a Cylindrical Hole with an Upstream Crescent-Shaped Block in Linear Cascade

“…The continuity equation discretization uses the Rhie-Chow scheme. The numerical works [20][21][22]29] for cylindrical holes with or without the crescentshaped block in flat-plate conditions have already shown that the predicted results of laterally averaged cooling effectiveness agree well with the experimental data in [19]. The predicted total pressure loss coefficient profile along the spanwise direction at M = 2.2 is further provided in this study compared with the experimental data in [30], demonstrated in Figure 7.…”

“…Compared with the simple ramp design and the complicated sanddune-inspired block concept, Zhang and Wang [19] evaluated the superiority by placing a two-dimensional crescent-shaped block upstream of a cylindrical hole. Although the crescent-shaped block was originally put downstream of a cylindrical hole [20], it could still greatly raise the cooling effectiveness. Zhang et al [21] conducted a sensitivity analysis on the geometrical parameters of the crescent-shaped block.…”

Effect of lid height and blowing ratio on film cooling effectiveness of a novel lidded hole configuration

“…Placing an obstacle downstream the injection hole is one of the new ways to enhance film cooling flow distribution on the cooled surface. For example, crescent-shaped block configuration promises significant improvement in film cooling as reported in the research work of Khorsi et al 20 Recently, Zhang et al 21 investigated the effect of crescent-shaped block streamwise position on flat plate film cooling characteristics. Hefang et al 22 numerically studied the effects of four types of winglet vortex generators upstream of the film hole on film cooling performance.…”