Total cooling effectiveness on a staggered full-coverage film cooling plate with impinging jet

In the present study, total cooling performance was experimentally investigated on a full-coverage film cooling plate with an impingement jet cooling array. The detailed temperature distributions on the film cooled surface were measured using an infra-red thermographic technique. The test plate was made of polycarbonate (k=0.2 W/m•K) and an array jet impinged underneath the test plates. The measured cooling effectiveness is a combined result of film cooling on the surface and convective heat transfer by a jet impingement array underneath the test plate. The diameter (d) of both film cooling and impingement jet cooling holes was 5 mm. Both the streamwise and spanwise hole spacing-to-hole diameter ratios (p/d) were 3 on the film cooled plate and impingement nozzle plate. The inclination angles of the film cooling holes and impingement jet holes were 35° and 90°, respectively. The holes on each plate were arranged in a staggered pattern. The jet Reynolds number based on the hole diameter varied from 3,000 to 7,000 and the equivalent blowing rate (M) changed from 0.3 to 0.7. The combined cooling effectiveness was measured by changing the gap distance between the jet plate and the film cooling plate from 1 to 5 times the hole diameter. The staggered film cooling hole arrangement showed a higher film cooling effectiveness than the inline film cooling hole arrangement. As the blowing rate increased, the cooling effectiveness decreased on the front part of film cooling plate for a fixed height to diameter ratio (H/d). The effect of H/d on the total cooling effectiveness was not significant for the fixed blowing rate (M) in the tested range.