Simulation of Backward Film Cooling at Gas Turbine Operating Conditions With and Without Mist Injection

Abstract

The cooling of gas turbines is critical for engines’ efficiency as well as safety and lifetime. Film cooling has been used to cool the turbine blades for many years. The main issues related to film cooling are its poor coverage, aerodynamic loss, and increase of heat transfer coefficient due to strong flow mixing. To overcome these problems, film cooling with backward injection has been found to produce a more uniform cooling coverage under low pressure and temperature conditions and with simple cylindrical holes. The performance of film cooling with backward injection at gas turbine operating conditions is studied with numerical simulation in this paper. Effects of the blowing ratios and angles are examined. It is seen that the cooling coverage is generally much more uniform by using backward injection at gas turbine operating conditions, and in some cases the film cooling effectiveness can be almost doubled when compared to forward injection. The backward injection also shows its advantage when the blowing angle and blowing ratio change. However, mist (droplets) injection does not affect the cooling performance of the backward jet at the conditions under study. The best case of film cooling in this study is the fan-shaped hole with backward injection.