Influences of groove configuration and density ratio on grooved leading-edge showerhead film cooling using the pressure sensitive paint measurement technique

Abstract

In response to the cooling requirements of high adiabatic cooling effectiveness and low convective heat transfer coefficient on the outer wall of the showerhead leading-edge of the turbine vane, a groove configuration is set near-stagnation region, and a grooved leading-edge showerhead cooling structure is designed. Using the steady-state pressure-sensitive paint technology as the measurement method, the interference effect of the groove configuration on the leading-edge showerhead film cooling was experimentally investigated. The influences of the depth and width of the groove on the adiabatic cooling effectiveness of the showerhead leading-edge were compared and analyzed in detail. The present study investigated the adiabatic cooling effectiveness of the showerhead leading-edge with counter-inclined film-holes under varied momentum flux ratio MR varies in the wide range of 0.09–6.04. The influence of coolant mass flow rate on the showerhead cooling effectiveness for the original leading-edge with counter-inclined holes was studied thoroughly; that is, the area-averaged adiabatic cooling effectiveness increases first, then decreases, and then increases again as MR increases. The arrangement of the grooves also enables the grooved structure to ensure the trend mentioned above. Compared with the original case, the effects of the groove on the showerhead cooling effectiveness are mainly reflected in the coolant retention within the groove, the jet-out and superimposition of the downstream of the outer rows. As the MR continues to increase, the grooved case is more likely to have a counter-inclined film distribution in advance, and the turning point of the adiabatic cooling effectiveness drops first and then rises earlier than the original case at a higher MR. The film-coverage of the shallow-grooved case is slightly better than that of the deep-grooved case. The widening of the groove width is not conducive to improving the film-coverage of the showerhead leading-edge. On the contrary, the interference of flow within the groove on the outflow causes a negative effect under lower coolant injection rates. The influence of the density ratio on the showerhead cooling effectiveness of the grooved leading-edge is similar to the original case. At the constant MR, the cooling effectiveness increases as the density ratio increases, and the core region of film-coverage downstream is broader and more extended.