FILM COOLING EFFECTIVENESS MEASUREMENTS ON A CMC-SIMULATED FLAT PLATE

Ceramic matrix composites (CMC) are high temperature materials that can allow higher operating turbomachinery engine temperatures with less coolant required. One method of fabricating ceramic matrix composites is by weaving fibers into the shape of an airfoil. Generally, CMC fiber tows are assembled with various weave patterns, but this uneven surface could introduce aerodynamic losses, and it will be necessary to determine the best film cooling hole arrangement for minimal thermal engine efficiency loss. As part of an effort to assess the impact of geometric constraints of CMC implementation relative to metallic high pressure turbine blades, an experimental study was performed to investigate the effect of film cooling on a CMC-like surface roughened flat plate. Film cooling effectiveness measurements were acquired on a large-scale surface with a ceramic matrix composite weave pattern and on a smooth surface for comparison. A single row and a 2-row cooling hole arrangement were investigated with different hole sizes. Infrared thermography data was acquired at several Reynolds numbers and blowing ratios. Results showed that the effect on span averaged film cooling effectiveness was small between a weave surface pattern and a smooth surface, while hole spacing dependence had a much stronger effect.