Experimental Investigation on the Heat Transfer of a Leading Edge Cooling System: Effects of Jet-to-Jet Spacing and Showerhead Extraction

Abstract

An experimental survey of a leading edge cooling scheme was performed to measure the Nusselt number distribution on a large scale test facility simulating the leading edge cavity of a pressure turbine blade. Test section is composed by two adjacent cavities, a rectangular supply channel and the leading edge cavity. The cooling flow impinges on the concave leading edge internal walls, by means of an impingement array located between the two cavities, and it is extracted through shower-head and film cooling holes. The impingement geometry is composed of a double array of circular holes. The aim of the present study is to point out the effects on the heat transfer coefficient of the radial jet pitch (y/d = 3 to 5) and the tangential jet pitch (x/d = 3 to 5). Moreover the influence of the shower-head extraction on the heat transfer distribution is investigated. Measurements were performed by means of a transient technique using narrow band Thermo-chromic Liquid Crystals (TLC). Jet Reynolds number was varied in order to cover the typical engine conditions of these cooling systems (Rej = 15000–45000). Results are reported in terms of detailed 2D maps, radial and tangential averaged Nusselt numbers.