Turbine nozzle endwall aero-thermal characteristics under combustor louver coolant with interface cavity

Abstract

Targeting on combustor-turbine interface cooling system of combustor louver coolant and interface cavity, the endwall film cooling and heat transfer characteristics as well as the vane phantom cooling performance of a nozzle guide vane are investigated by solving the Reynolds-Averaged Navier-Stokes equations, and the secondary flow structure at endwall region are analyzed. The results show that most of the louver coolant leads to the core cooling region on the endwall after recirculating in the cavity with the cavity vortex, while a minority of the louver coolant escapes from the cavity vortex and forms the outer endwall cooling region limited by the horseshoe vortex. Under a certain mainstream flow condition, the endwall cooling performance and net heat flux reduction (NHFR) only depend on the mass flow ratio (MFR) of louver coolant instead of blowing ratio (BR). With increasing louver BR, the coolant mainly leads to the increase of the width and film cooling effectiveness of the core region at high MFR, but it leads to increasing cooling effectiveness of the outer region at low MFR. When the louver MFR increases from 0.25 % to 1.91 %, the averaged endwall cooling effectiveness at z/Cax = 0.1 is increased from 0.04 to 0.21. The NHFR of the core and outer cooling region reaches 0.3 and 0.1, respectively. The pressure and suction side horseshoe vortexes cause two protection failure regions, and its NHFR further decreases with increasing BR. At high MFR, the heat transfer in the low Nusselt number regions resulted by cavity vortex separation is further weakened with the increase of BR, and the region is enlarged toward two sides of the cascade. When MFR = 1.91 %, the Nusselt number of the high heat transfer region at z/Cax = 0.7 decreases from 2200 to 2000, and the averaged NHFR of fore part endwall reaches up to 0.2. This paper provides guidance for endwall cooling configuration design by taking the compound effect of the combustor-turbine interface cooling scheme into account.