Turbine Stator Well CFD Studies: Effects of Coolant Supply Geometry on Cavity Sealing Performance

The increase of aero engines performance through the improvement of aerodynamic efficiency of main annulus flow is becoming more and more difficult to achieve. However there are still some devices that could be improved to enhance global engine efficiency. Particularly, investigations on the internal air cooling systems, may lead to a reduction of cooling air with a direct benefit to the overall performance. At the same time, further investigations on heat transfer mechanisms within turbine cavities may help to optimize cooling air flows saving engine life duration. This paper presents a CFD study aimed at the characterization of the effects of different geometries for cooling air supply within turbine cavities on wall thermal effectiveness and sealing mass flow rate. Several sealing air supply geometries were considered in order to point out the role of cooling air injection position, swirl number and jet penetration on the cavities sealing performance. The study was set up on a two-stage axial turbine rig developed in a research programme on internal air systems funded by EU (Main Annulus Gas Path Interactions - MAGPI). Steady state calculations were performed using two different computational domains: the first consists in a sector model of the whole turbine including the second stator well, while the second is a cut-down model of the stator well. Thanks to the simplified geometry of the test rig with respect to actual engines, the study has pointed out clear design suggestions regarding the effects of geometry modification of cooling air supply system.