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

应用项目的目的是增加对多通道冷却通道内流动物理及其操作的理解。在系统研究的框架内，将分析肋片冷却通道内气膜冷却孔的位置对离散肋片几何形状的影响。由此得到的知识将导致内部换热的改善，从而导致叶片冷却。先前在椅子上的工作显示了冷却空气抽出对特定肋骨位置的内部换热的影响。可以预期的是，在更像发动机一样的配置中，具有多个连续的肋段和冷却空气抽气，单个孔的效果将相互影响并可能放大。此外，实际涡轮叶片中的肋条具有导致肋条通道内二次流动的倾斜度。与直肋相比，湍流的增加和附加的涡流导致局部强化的换热。因此，出现了一个问题，即轴向和横向上的特定冷却孔位置是否会对二次流动和换热产生积极的影响。对于斜肋和V形肋片，将采用成功的孔位定位概念，研究的主要问题是，冷却抽风位置对以二次流为主的肋片通道内的流场有何影响，以及这对换热有何影响。这些问题将在连续肋骨节段的相互作用下进行审查。这项工作的结果将加强对肋片周围流场和冷却通道内气膜冷却抽气相互作用的物理理解。如果满足预期，研究结果可以应用到未来的燃气轮机冷却系统设计规则中。这将提高现有冷却空气和整个冷却系统的利用率。涡轮机将获得更高的效率和使用寿命。对于整个系统来说，这将导致更低的燃油消耗和排放。

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.