Effect of Periodic Wake Passing on Film Effectiveness of Inclined Discrete Cooling Holes Around the Leading Edge of a Blunt Body

Abstract

Detailed studies are conducted on film effectiveness of inclined discrete cooling holes around the leading edge of a blunt body that is subjected to periodically incoming wakes as well as free-stream turbulence with various levels of intensity. The cooling holes have a configuration similar to that of a typical turbine blade and are angled at 30 and 90 deg to the surface in the spanwise and streamwise directions, respectively. A spoked-wheel-type wake generator is used in this study to simulate periodically incoming wakes to turbine blades. In addition, two types of turbulence grid are used to elevate a free-stream turbulence intensity. We adopt three blowing ratios of the secondary air to the mainstream. Most of the dominant flow conditions are reproduced in this study, except for the air density ratio of the secondary air and the main stream. For each of the blowing ratios, wall temperatures around the surface of the test model are measured by thermocouples situated inside the model. The temperature is visualized using liquid crystals to obtain traces of the injected secondary air on the test surface, which consequently helps us interpret the thermocouple data.