Influence of local air extraction due to film cooling on the flow field and heat transfer in cooling channels with variation of rib geometry and position

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The goal of the applying project is to increase the understanding of flow physics in a multipass cooling channel and its manipulation. In the frame of a systematic investigation the influence of the position of film cooling holes within a ribbed cooling channel for discrete rib geometries will be analyzed. The resulting knowledge will lead to an improvement of internal heat transfer and therefore blade cooling.Previous work at the Chair shows the influence of the cooling air extraction on the internal heat transfer for specific rib positions. It can be expected, that in more engine-like configurations, with multiple successive rib segments with cooling air extraction, the effects of the single holes will influence and possibly amplify each other. Further the ribs in real turbine blades have an inclination leading to a secondary flow within the rib passage. The increased turbulence and additional vortices result in a locally intensified heat transfer in comparison to straight ribs. Therefore the question arises, if a specific position of the cooling holes in axial and lateral direction will allow a positive influence of the secondary flows and heat transfer. The successful concept of the hole positioning will be adopted to inclined and V-type ribs.The main questions of the investigation are, how the position of the cooling air extraction can manipulate the flow field within the rib passage, which is dominated by the secondary flow, and what this means to the heat transfer. These questions will be examined under the interaction of successive rib segments. The results of the proposed work will enhance the physical understanding of the interaction of the flow field around ribs and the film cooling extraction within a cooling channel. If the expectations are fulfilled, the results derived for the research can be implemented into future design rules for gas turbine cooling systems. This will improve the usage of the available cooling air and whole cooling system. A higher efficiency and life time of the turbine will be achieved. For the overall system this results in lower fuel consumption and emissions.