Transonic vane film cooling with shaped sweeping jet design

Abstract

The sweeping jet (SJ) presents promising potential for film cooling due to its periodic, self-excited flow behavior. The shaped sweeping jet (SSJ) design features a compact structure and has demonstrated superior cooling performance compared to conventional holes under low-speed conditions. This study further explores the SSJ cooling performance on a transonic vane's pressure and suction surfaces. Experiments were conducted to evaluate its cooling performance and reveal the effects of blade curvature and pressure gradient under engine-relevant Mach numbers (exit Ma = 0.84). The adiabatic cooling effectiveness of the SSJ and the baseline 777 holes was measured using the fast-responding pressure-sensitive paint (Fast-PSP) technique at blowing ratios of M = 0.5–3.0. The oscillating frequency of the SSJ and its Strouhal number were determined through velocity fluctuation analysis. Experimental results consistently show enhanced cooling effectiveness on the pressure surface for the SSJ compared to 777 holes, with the maximum improvement of 85 % observed at M = 2.5. Due to stronger compressibility effects on the suction surface, the cooling effectiveness of the SSJ increases more significantly with rising blowing ratios compared to the pressure surface. Numerical simulations reveal that the SSJ generates a smaller recirculation zone than the 777 hole. The alternating vortices formed during the sweeping process enhance lateral film distribution. Additionally, the total pressure loss coefficient of the SSJ remained comparable to that of the 777 holes, with a maximum increase of 6.11 %. These results contribute to the understanding of SJ film cooling and support the potential application of SSJ in turbine film cooling design.