Effusion Cooling: The Influence of the Number of Holes

Abstract

Experimental measurements of the overall cooling effectiveness for full-coverage discrete hole effusion cooling are presented for a wide range of practical geometries and for a density ratio between the coolant and combustion gases of 2.5. The influence of the number of holes per unit surface area was investigated at two fixed total hole areas or design pressure loss. These were a pressure loss of 3 and 0.1 per cent for a relatively low coolant flowrate per unit surface area. Hole configurations suitable for combustor wall cooling were investigated with hole sizes from 1.4 to 0.6 mm at 3 per cent design pressure loss and 1.3 to 3.3 mm at 0.1 per cent design pressure loss. Increasing the number of holes and increasing the hole diameter were shown to increase the cooling effectiveness through improved film cooling. Major reductions in current combustor wall cooling flows were demonstrated for some full-coverage effusion geometries.