New Thermal Protection Concepts for the Next Generation Gas Turbines and Hypersonic Vehicles

Abstract

Abstract : Thermal protection of gas turbine blades, combustors and some rocket nozzles is generally provided by thin superficial layer coatings of yttria-stabilized zirconia (YSZ). This material, deposited by either electron-beam physical vapor deposition or plasma-spraying, has exceptionally low thermal conductivity up to high temperatures but its resistance to radiative heat transport is not known in any detail. Although oxides with still lower thermal conductivity at high temperatures than YSZ have been discovered, the mechanisms that limit radiative transport in coatings have yet to be clarified. The research performed under this contract has focused on identifying the radiative transport through current thermal barrier coatings and how this changes with long term exposure at high temperatures as well as underexposure to CMAS attack. Together with detailed modeling of combined radiative and thermal conductive heat transfer, the materials requirements and concepts for the next generation coatings have been identified.