The described subject matter relates generally to gas turbine engines and more particularly, to arrangements for separating hot and cold flows in gas turbine engines.
Compact engines require closer packing of components, which in turn requires more crossing of hot and cold gas flows. Without adequate thermal protection, seals, and insulation between these flows, smaller engines suffer from a loss of efficiency. One system developed for certain engines is the mid-turbine frame (MTF), also known as the turbine center frame (TCF) or interturbine frame. This can be disposed between intermediate stages of the turbine section and can have numerous components serving a variety of functions, including as bearing support, engine backbone, combustion gas flow path, coolant flow path, among others.
Despite tight sealing of the various flows, efficiency gains expected from increased combustion temperatures are not always realized due in part to hot section components being disposed in close proximity to cold section components. As engines are made smaller, the clearances between components, including in the mid-turbine frame area also become tighter. Additional measures must therefore be taken to maintain flow separation and account for higher thermal gradients.