An Investigation of an Impingement / Pin-Fin Cooling System for Gas Turbine Combustor Applications

Abstract

Pin-fin cooling geometries are used extensively in gas turbine engine components, typically in combination with film-cooling and thermal barrier coatings. The cooling performance of this cold-side arrangement is an important factor in maintaining hot-section components below prescribed life-limiting temperatures. At a time when engine manufacturers are pursuing combustor designs that require a reduced coolant flow, robust aerodynamic and heat transfer correlations, as well as the physical insight provided by a deeper understanding of the flow processes, are essential to efficient design. In this paper both experimental and computational findings are reported for the performance of a combustor pin-fin cooling system that employs a single row of impingement feed-holes. The geometry is representative of that employed in a double-skin combustor cooling system. The data includes spatially resolved end-wall heat transfer measurements, and hot-wire traverse data for the coolant velocity and turbulence parameters. Heat transfer measurements have been obtained for the cold-side of the hot-skin, and include the impact of a gap between the cold-skin and tips of the pin-fins. The flow conditions within the pin-fin geometry can be divided between an impingement zone immediately adjacent to the feed-holes, and a fully-developed zone further downstream. In general, the impingement zone is characterised by strongly varying flow and heat transfer behaviour up to approximately six pin-fin rows from the feed-hole centre-line, and then sensibly repeating conditions within the pin-fin array thereafter downstream. The impact of the cold-skin gap is to redistribute the coolant away from the hot-skin, leading to a reduction in the hot-skin heat transfer coefficient in the developed zone. Reynolds averaged Navier-Stokes (RANS) simulations of the flow within the experimental geometry have been conducted and compared to the experimental results. Various standard turbulence models have been considered. Based on this comparison recommendations are made regarding the most appropriate computational modeling approach.