Impingement Heat Transfer on a Target Plate with Film Cooling Holes

Detailedheat-transferdistributionsarepresentedforanarray ofjetsimpinging onatargetplatewithastaggered array of e lm cooling holes. The e ow impinges on the target plate through a row of impingement holes and exits the channel from the sides and through the e lm holes. The top plate has 12 rows of impingement holes, and the target platehas11 rows ofe lm holes. Theimpingementholes and the e lm holes have thesame diameterandarestaggered such that the air from the impingement hole does not exit directly through the e lm hole. The setup is typical of an impingement/transpiration cooled gas turbine airfoil. Additional to the e ow exiting through the e lm holes, there is an exit for crosse ow after impingement. The exit opening of the impingement channel is changed to provide three different spent air exit directions. The detailed heat-transfer coefe cient distributions were measured using a transient liquid crystal technique. Results are presented for a range of jet Reynolds numbers between 0.4 ££ 10 3 and 2.0 ££ 10 4 with different exit e ow orientations. Heat-transfer results for the target plate with e lm holes are compared with those without e lm holes under the same e ow conditions. Film extraction reduces crosse ow effects on jet impingement heat transfer. However, overall averaged heat-transfer rates on the target surface appear less affected by presence of e lm hole for cases where the crosse ow is generated in only one direction.