Experimental Investigation of the Effects of Thermal Barrier Coating on Twisted Blade Full Film Cooling

Abstract

Film cooling and thermal barrier coating technologies are often used in thermal protection of aero-engine turbine blades. But the film-hole structure can be often affected by thermal barrier coatings (TBC) spraying, resulting in the variations of aerodynamic and thermal performances of film cooling. In this paper, adiabatic film cooling effectiveness distribution contours of twisted vanes with multi-row film cooling holes in fan-shaped cascade tunnel were obtained by PSP technology. The effects of TBC on twisted vanes film cooling effectiveness were studied, which was sprayed by electron beam physical vapor deposition (EB-PVD). Three typical density ratio (DR) of 1.0, 1.5 and 2.0 and three mass flow ratio (MFR) of 8.92%, 10.45% and 12.21% were test. The air was selected as the mainstream, nitrogen, carbon dioxide and 15% sulfur hexafluoride mixd with 85% argon were independently selected as secondary flow to produce three density ratios of 1.0, 1.5 and 2.0. The results indicate that TBC improves film cooling effectiveness on suction surface by 6.2%–16.67%, and significantly reduces the film cooling effectiveness on the leading edge (37.7%–52.7%) and gill areas of the pressure surface (28.8%–32%). In these three regions, the difference between vanes with and without TBC is slightly affected by the change of MFR, and gradually decreased with the increase of density ratio. The film cooling effectiveness of the pressure surface near the trailing edge is less weakened by the TBC, where the maximum reduction is 8.92%. Compared with the cylindrical hole rows, TBC has less impacts on film cooling effectiveness at fan-shaped hole rows.