Wall thickness and injection direction effects on flat plate full-coverage film cooling arrays: Adiabatic film effectiveness and heat transfer coefficient

Adiabatic film effectiveness and heat transfer coefficient were determined for a full-coverage effusion cooled surface which simulates a portion of a gas turbine blade. Adiabatic film effectiveness and heat transfer coefficient were measured with low thermal-conductivity plastics using pressure sensitive paint and steady liquid crystal, respectively. The blowing ratio ranged from 0.5 to 2.5 with the density ratio of DR = 1.5. Geometrical parameters investigated included wall thickness (from 1.0D to 2.5D) and jet-injection directions (forward and backward injections). Local, laterally-averaged, and area-averaged adiabatic film effectiveness and heat transfer coefficients were shown to illustrate the geometrical parameter effects. Comparison of net heat flux reduction was conducted to provide an overall heat transfer estimation. Results showed that decreasing wall thickness results in opposite impacts for forward and backward injections. Also observed was that adopting backward injection for thin full-coverage effusion plate provided the highest adiabatic film effectiveness, heat transfer coefficient, and net heat flux reduction for most blowing ratios.