Evaluation of Particulate Deposition Effects on Film Cooling Using Conjugate Heat Transfer Methods: An Experimental and Numerical Study

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 influences the overall cooling performance by changing the surface geometric and thermal conditions. In this study, an experimental and numerical combined methodology was used to evaluate the deposition effects on film cooling from a row of holes on conductive flat plates. Cylindrical holes with simple and compound holes that are extensively used in today's modern engines 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 better understand the coupling effects of film cooling with deposition and their interaction with solid walls. Furthermore, the isolated effects of deposition on adiabatic film cooling and heat transfer were examined, allowing for a better understanding of which factor dominates the resulting combined effects. Inspection of overall cooling effectiveness on the wall backside revealed that the deposition effects were 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.