Experimental evaluation of a turbine blade with potassium evaporative cooling

A new method of turbine blade cooling, the return-flow cascade, was developed in which vaporization of a liquid metal such as potassium is used to maintain the blade surface at a nearly uniform temperature. Turbine blades cooled using this technology may have lower blade temperature levels than those available with conventional air cooling and could result in higher firing temperatures or a choice of a wider range of materials for the hot-gas path. Condensation occurs remotely from the blade and enables heat rejection to alternative sinks such as low-pressure air or fuel. Experimental results are presented from testing of a potassium-cooled model blade in the rotating heat transfer rig at the Massachusetts Institute of Technology. An infrared detector capable of high scan rates was used to fully map the temperature distribution of a single heated rotating turbine blade. The functioning of the cascade is inferred from this temperature distribution and shows that a near-uniform blade temperature can be maintained by the evaporative cooling system.