Cooling of a Honeycomb Shroud Seal in Order to Reduce Oxidation

Abstract

As a result of continuous enhancement of the capability of it’s gas turbines, proposed uprated versions the SGT-100 engine were predicted have pre-mature oxidation of the honey-comb seal material above the CT1 blade. This would lead to an increase in over tip leakage and degradation of engine performance. A project to increase the service life of the honeycomb was started and various options considered. Initially a CFD analysis of the region was carried out in order to understand the flow field in the cavity surrounding the HP blade shroud, and hence the source of the high temperatures. Further CFD studies were carried out to assess the effect of applying cooling air into the cavity, and the optimal position to introduce such flow so it had maximum effect on the honeycomb temperatures. Modifications were then carried out to engine components to replicate cooling proposed by the CFD analysis and a series of engine tests with, and without the cooling were carried out. The Shroud temperatures were measured during engine operation by infra-red Pyrometry, which confirmed the effectiveness of the cooling modification.