Film cooling measurements on cylindrical models with simulated thermal barrier coating spallation

Detailed heat transfer coefficient and him effectiveness distributions are presented on a cylindrical leading-edge model with simulated thermal barrier coating spallation using a transient liquid crystal technique. Tests were performed in a low speed wind tunnel on a cylindrical model in a crossflow with two rows of injection holes, Mainstream Reynolds number based on the cylinder diameter was 1.009 x 10(5). The two rows of injection holes were +/-15 deg from stagnation. The film holes were spared four hole diameters apart and were angled 30 and 90 deg to the surface in the spanwise and streamwise directions, respectively, The simulated spallation cavities were rectangular in shape and had rounded edges. The simulated spallation was placed st two locations, 20-40 deg (S3) and 35-55 deg (S4), respectively. The cylinder surface was coated with thermochromic liquid crystals, and a transient test was run to obtain the heat transfer coefficients and film effectiveness. The effect of coolant blowing ratio was studied for blowing ratios of 0.4 and 0.8. Results show that the Nusselt numbers increase and film effectiveness values decrease with an increasing blowing ratio. An increase in freestream turbulence has a very little effect on Nusselt numbers but reduces the him effectiveness significantly at low blowing ratios. In general, presence of spallation enhances Nusselt numbers and produces a strong variation in film effectiveness distributions.