Experimental and Numerical Investigation of a Steam-Cooled Vane

Abstract

Closed circuit steam cooling of blades and vanes in modern gas turbines is a promising alternative to film-cooling using compressor air. This technology is becoming part of commercial gas turbines in combination with a steam turbine cycle. There is still a great demand for further development of steam-cooled vanes and blades. Thus, detailed experimental and numerical investigations of the thermal load of a steam-cooled test vane are the main topic of the paper presented. An experimental test rig has been set up, which consists of a rectangular duct containing a three-vane cascade. The central vane can be convectively cooled by supplying steam or compressor air to 22 straight radial cooling passages. The surface temperatures of the cooled vane are measured by application of temperature sensors and a thermographic visualization technique. For the present configuration sufficient cooling can be achieved for the main body of the vane, but, high thermal load has been detected in the thin trailing edge region. A parametric study of steam supply conditions has been performed. The measurements are used to create a data base for steam-cooled vanes, which can serve for the validation of numerical codes. The experimental investigations are accompanied by 3-D numerical investigations using the conjugate calculation technique. That means, the external hot gas flow and the steam flow in the cooling tubes are calculated directly coupled to the vane solid body, which is also part of the calculation. Thus, numerical prediction of the temperature field in the vane solid body is possible. The numerical results are in accordance with the experimental data although the external walls of the duct have been prescribed as adiabatic walls. The results show also a very high thermal load at the trailing edge.