Piv Investigation of Internal Cooing Channels for Gas Turbines, with 45 Degrees Inclined Ribs

The object of this study is to characterize the aero-thermal performance of a rectangular turbine blade cooling channel for gas turbines equipped with turbulence promoters, square section ribs, inclined at 45 degrees with respect to the main flow direction. With this aim, a P.I.V investigation of the flow field within an inter-rib space inside four cooling channel models has been done. The presence of the ribs aims at ripping the boundary layer in order to increase the turbulence level and thus enhance the heat transfer between the channel walls and the coolant air. Four different configurations are reported, based in two parameters: the inter-rib distance, normalized with respect to the rib height (?/h=7.5 and ?/h=15), and the presence of ribs on one or on two opposed walls. The measurements were carried out for a Reynolds number of 40000, representative for this kind of passages. Using Particle Image Velocimetry, mean flow field patterns are displayed along four mutually perpendicular planes in the inter-rib space, to present the three dimensional behavior of the flow in the projected measurement planes. Fluctuating flow features are reported for every measurement plane. Liquid Crystal Thermography was used for the thermal measurements on the ribbed walls, giving Nusselt number contours plots for every configuration. The link between the aerodynamic field and cooling capability is shown by superposing the obtained streamlines in a plane parallel to the inter-rib wall on the Nusselt contours. The acquired data are also a contribution to a database for testing numerical codes.