Conjugate Heat Transfer of Cylindrical and Trenched Film Cooling Designs With Array Jet Impingement

Abstract

A numerical film cooling study involving different external cooling designs, thermal barrier coating (TBC) and internal cooling methods is performed. The steady Reynolds Averaged Navier Stokes (RANS) equations are solved including conjugate heat transfer (CHT). The heat transfer coefficient and material properties of the TBC and vane material lead to a proper scaling of the Biot number with respect to real engines. The cooling efficiency of the external surface and of the wall interface between TBC and vane are evaluated. Three film cooling designs, namely standard effusion hole film cooling as well as transverse and optimized trenches are investigated. Moreover, the effect of array jet impingement and convective channel cooling is investigated onto the external and interface cooling efficiency. The jet Reynolds number of the impingement and effusion cooling is varied between 3100–12300 at blowing ratios between 0.3 and 1.2. The main-stream Reynolds number varied between 4500 and 11000 depending on the tested density ratio. The external cooling efficiency of both trench designs showed to be superior to the standard effusion case. With respect to the interface cooling efficiency, there was an improvement in efficiency of 0.1 visible for the trenched designs compared to the standard effusion hole design. Moreover, flow ingestion into the trenches and the external heat flux and heat transfer coefficient are investigated.