Abstract
A significant challenge of offering adequate film cooling for gas turbine hot components in practical operation is deposition induced by impurities from the intake air and fuel, which changes the surface geometric and thermal conditions. In this study, an experimental and numerical combined methodology was used to evaluate deposition effects on film cooling from a row of holes on conductive flat plates. Cylindrical holes with simple and compound holes were investigated to assess the sensitivity of their overall cooling effectiveness to deposition for coolant injection ratios of 0.5–2.0. Flow physics and thermal fields were analyzed to understand the coupling effects of film cooling with deposition and their interaction with solid walls. Further, the isolated effects of deposition on adiabatic film cooling and heat transfer were examined, allowing for better understanding of which factor dominating the resulting combined effects. Inspection of overall cooling effectiveness on the wall backside revealed that the deposition effects was strongly linked to coolant jet behaviors, which were determined by both the coolant injection ratio and the hole orientation angle. Quantitative comparisons showed that deposition decreased overall cooling effectiveness by 22% on the flat plate cooled by the compound-angled hole with the lowest blowing ratio of 0.5, while it increased overall cooling effectiveness from the simple hole by 38% at a higher blowing ratio of 1.5. The results reported for the current work provide guidance on how to choose orientation angles for film cooling design where deposition problems are accounted for.
