Internal Cooling at the Trailing-Edge of a High- Pressure Gas Turbine Blade

Abstract

The efficiency of a gas turbine engine tends to be increased when its turbine blades are operated at higher temperatures. In turn, this requires the adequate cooling of these turbine blades (for both rotors and stators, collectively termed “airfoils”). Of specific concern in this study is the cooling at the trailing- edge of the airfoils. However, there exists limited space for cooling due to a requirement for a thin trailing-edge. A combination of perforated blockage plates and a pin-fin array (a “blockage pin-fin” configuration) is particularly focused on here. Such a configuration has been previously discounted due to a presumed poor thermal performance ( hTP < 1.0). This thesis demonstrates that the thermal performance has been misrepresented in part due to a misunderstanding of flow behaviours present in the configuration. To this end, a series of experimental tests are undertaken using particle image velocimetry, oil-dye flow visualization, and thermochromic liquid crystal paints. The new results show that a thermal performance greater than one (i.e., hTP > 1.0) can be achieved for a blockage pin-fin configuration. Despite previous studies concluding otherwise there may be merit in the use of a blockage pin-fin configuration for internally cooling the trailing-edge of a turbine blade. Further, a unique flow topology, present in a blockage pin-fin configuration was revealed. Such a flow, termed as a “jet-pin” flow, and its interactions has been previously unidentified or misinterpreted.