Large eddy simulation of compound angle hole film cooling with hole length-to-diameter ratio and internal crossflow orientation effects

摘要

Compound angle hole film cooling with varying length-to-diameter ratio and internal crossflow orientations is investigated by large eddy simulation (LES). The film density ratio is 1.5, and the blowing ratio ranges from 0.4 to 1.2. The compound angle of 45 and three length-to-diameter ratios (L/D) from 0.5 to 5 are chosen for the simulations. In addition to the vertical inflow through the plenum, internal crossflow orientations that are perpendicular to and parallel to the mainstream flow are investigated. The prediction accuracy is validated by the reported hydrodynamic data and present film effectiveness data measured by pressure sensitive paint (PSP). Results show that compound angle hole film effectiveness generally shows a decreasing trend as length-to-diameter ratio increases, which is contrary to the cylindrical hole. This is associated with the fact that length-to-diameter ratio influences the in-tube flow behavior, formation of Kelvin-Helmholtz(K-H) structures, and development of single asymmetric main vortex (SAMV). The internal crossflow orientation is demonstrated to have a significant effect on the in tube flow behavior and the film cooling effectiveness. The perpendicular-counter flow and parallel-inline flow cases are found to provide more uniform hole exit velocity distributions than other internal crossflow orientations and vertical inflow case. Also found is that uniform hole exit velocity distribution provides favorable influence on the film effectiveness. (C) 2017 Elsevier Masson SAS. All rights reserved.