Abstract

Detached eddy simulation has been carried out to study a three-dimensional trailing-edge (TE) cutback turbine blade
model with five rows of staggered circular pin-fin arrays inside the cooling passage, in order to evaluate the cooling
performance in relation to coolant ejection slot angle. Simulations were performed by adopting a shear-stress transport
k-ω turbulence model, and the effects of three different ejection slot angles 5°, 10° and 15° were investigated in terms
of the characteristics of adiabatic film-cooling effectiveness, coefficient of discharge, and vortex shedding frequencies,
respectively. The results obtained have shown that the TE cutback blade cooling with a 5° coolant ejection slot angle
produced a better heat transfer coefficient than the other two ejection slot angles tested. The distributions of adiabatic
film-cooling effectiveness along the cutback walls were found to be sensitive to the coolant ejection slot angle, e.g. the
increase of ejection slot angle to 15o yielded near unity of cooling effectiveness along the entire breakout walls,
whereas the decrease of ejection slot angle caused a drastic decay of cooling effectiveness after the maximum
effectiveness has been reached. Of the three angles studied, a TE cutback blade model with a 15° ejection slot angle
produced an optimum film-cooling effectiveness. In the breakout region, vortex shedding was observed along the
shear layer between the hot gas and the coolant airflow. The shedding frequencies were evaluated to be 2.93, 2.21,
and 2.18 kHz for the ejection slot angles of 5°, 10° and 15°, respectively. The findings from this study could be useful
to improve existing TE cutback turbine blade design to achieve optimum film-cooling performance