A new perspective on internal turbine blade cooling by perforated blockages and pin-fins

Abstract

Abstract The cooling configuration, sequentially combining perforated blockages (forming blockage jets) and a pin-fin array inside the trailing-edge of a turbine blade has been perceived unsuitable due to the presumed inferior thermal performance (η < 1.0). In the present study, we provide a new perspective on this particular cooling configuration, based on fluidic mechanisms, newly established in a better representative setup for blockage jets aligned with pin-fins, accounting for relevant heat transfer surfaces. To this end, heat transfer on the blockage, pin-fin, and end-wall surfaces was measured at a selected Reynolds number of ReD = 26,000 using a thermochromic liquid crystal technique. Flow field mapping by particle image velocimetry and oil-dye flow visualization were supplementally performed. We demonstrate, contrary to previous studies that the thermal performance of the blockage pin-fin configuration can be e.g., η = 1.35 if the blockages and pin-fins are arranged to maximize both elements' thermofluidic advantages. Our data further suggests that unlike conventional pin-fin configurations subjected to uniform coolant stream, the blockage pin-fin configuration can offer a better performance with fewer pin-fin rows used.