Turbine Nozzle Guide Vane Endwall Film Cooling and Vane Phantom Cooling Performances at Various Blocked Film Hole Configurations

Abstract

Due to the deposition of TBC materials, partial film hole blockage is commonly observed in realistic turbine cascades, and the blockage mainly concerns on the trailing edge of the film holes. In the double-row discrete film hole layouts, endwall profiles may lead to variations between upstream film hole blockage (row 1) and downstream film hole blockage (row 2). Therefore, various blocked film hole configurations of this double-row discrete film hole layout are considered in this paper, specifically common holes (CH), upstream blocked holes (UBH+DCH), downstream blocked holes (UCH+DBH), and fully blocked holes (FBH). The aerothermal performance between simplified flat endwall and convergent contoured endwall was comparatively analyzed, aiming to assess the applicability of the corresponding findings regarding film hole blockage drawn from studies on simplified flat endwall to those on realistic turbine endwall and provide more insightful references for industrial designers. Based on the double-coolant temperature model, the film hole discharge coefficient (Cd), endwall film cooling effectiveness (η), vane PS phantom cooling effectiveness, and total pressure loss coefficient (TPLC) were calculated and discussed at the design coolant supply pressure condition. Results indicated that partial film hole blockage is pernicious to coolant flowrate, endwall film cooling, and vane PS phantom cooling performances, and thus, the geometric defects of film holes should be adequately considered as part of the film cooling layout designs.