Turbine Stator Well CFD Studies: Effects of Cavity Cooling Air Flow

Abstract

The improvement of the aerodynamic efficiency of gas turbine components is becoming more and more difficult to achieve. Nevertheless there are still some devices that could be improved to enhance engine performance. Further investigations on the internal air cooling systems, for instance, may lead to a reduction of cavities cooling air with a direct beneficial effect on engine 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 some CFD preliminary studies conducted on an two-stage axial turbine rig developed in a research programme on internal air systems funded by EU, named the Main Annulus Gas Path Interactions (MAGPI). Each turbine stage consists of 39 vanes and 78 rotating blades and the modelled domain includes both the main gas path of the two turbine stages and the second stator well. Pre experimental tests CFD computations were planned in order to point out the reliability of numerical models in the description of the flow patterns in the main annulus and in the cavities. Several computational meshes were considered with steady and unsteady approaches in order to assess the sensitivity to computational approach regarding the evaluation of the interactions between main annulus and disk cavities flows. Results were obtained for several cavities cooling air mass-flow rates and data were further analyzed to investigate the influence of the sealing flow inside the main annulus. MAGPI project is a 4 years Specific-Targeted-Research-Project (2007–2011) and its consortium includes six universities and nine gas turbines manufacturing companies. The project is focused on the analysis of interactions between primary and secondary air systems achieving a novel approach as these systems have, up to now, only been considered separately. In particular one of the tasks of the project will focus on heat transfer phenomena and delivering experimental data which will be used to validate the advanced design tools used by industries (CFD codes and correlative formulations).