Heat Transfer in 3D-Vane-Passages - Systematic Generation and Investigation of Contoured Vane-Endwall Geometries for Turbomachines Using the Ice Formation Method

研究项目Wärmeübergang在3D-Schaufelkanälen，已经设计了4年。目前的建议是该项目的第二阶段（第三和第四年）。在最初的两年里，考虑到叶片端壁上的传热减少，冰形成方法成功地用于创建新的叶片端壁结构。可以发现，与未成形的端壁相比，端壁结构的整体传热减少了11%。项目第二阶段的调查将显示进一步改善的潜力。我们将更详细地研究瞬态冰生长的各个方面。这将澄清，是否在冰层的增长过程中，其他有趣的拓扑结构将已经形成，其特征是局部最优的压力损失和/或传热行为。为此，在稳态之前的多个时间点的轮廓将通过实验来研究和分析熵产率、传热和压力损失。为了确定优化过程中不同初始条件对结果的影响，将以这些冰轮廓作为初始几何形状进行数值优化。由于很明显，叶栅前后的区域对端壁的传热也有很大的影响，因此冷却区域将扩展到这些区域。因此，提供了更多的自由度，并开发了拓扑结构，不仅在叶片之间的区域，而且在到上游和下游组件的过渡区域进行了优化。实验生成的冰等高线将用作具有多个目标函数的数值优化的初始几何形状，并将分析所得等高线。将数值研究扩展到燃气轮机的具体条件，将保证得到的轮廓不仅具有学术意义，而且对实际应用也很有用。此外，将研究通过叶片前面的狭缝额外注入冷却液的端壁轮廓，以了解当这些拓扑用作数值优化过程的初始几何形状时，注入对冰的拓扑结构有什么样的影响，以及会形成什么样的轮廓。通过对本项目生成的所有端壁轮廓进行总结性检查，确定端壁轮廓的改进拓扑元素，并给出端壁轮廓的建议。这些建议允许生成未来的端壁轮廓，这是更好地适应各自的应用程序。例如，使用端壁轮廓最小的传热显著减少所需的冷却空气，因此导致组件的寿命延长，并提高了涡轮的热效率。

The research project Wärmeübergang in 3D-Schaufelkanälen, has been designed for 4 years. The present proposal is now for the second phase (3rd and 4th year) of the project. In the first 2 years, the ice formation method was successfully used for the creation of novel vane-endwall configurations considering the heat transfer reduction on the vane endwall. Endwall configurations could be found, that show reduced integral heat transfer up to 11% compared to an uncontoured endwall. Investigations in the second phase of the project will depict further potential for improvement. Aspects of the transient ice growth will be investigated in more detail. It will be clarified, whether during the growth of the ice layer other interesting topologies will already be formed, which feature local optima in pressure loss and/or heat transfer behavior. For that purpose, contours at multiple points in time prior to the steady state will experimentally be investigated and analyzed in terms of entropy production rates, heat transfer, and pressure loss. In order to determine how different initial conditions in the optimization process affect its results, numerical optimizations will be conducted with these ice contours as initial geometries. Since it has become apparent that also the regions in front of and behind the cascade considerably influence the heat transfer at the endwall, the cooled area will be extended to these regions. Thereby, more degrees of freedom are provided and topologies are developed, that are optimized not only in the region between the vanes but also in the transition regions to the up- and downstream components. The experimentally generated ice contours will be used as initial geometries for numerical optimizations with multiple goal functions and the resulting contours will be analyzed. An expansion of the numerical investigations to gas turbine specific conditions shall guarantee that resulting contours are not only of academic interest but will also be useful for real applications.Furthermore, endwall contouring with additional injection of cooling fluid through a slot in front of the vanes will be investigated in order to see what kind of influence the injection has on the ice topology and what kind of contours develop, when these topologies are used as initial geometries for the numerical optimization process. By the use of a concluding inspection of all endwall contours generated in this project, improved topology elements for endwall contouring shall be identified and recommendations for the contouring of endwalls will be given. These recommendations allow to generate future endwall contours, which are better adapted to the respective application. For example, the use of an endwall contour for minimum heat transfer reduces the required cooling air noticeably and therefore leads to enhanced life time of the components and to a higher thermal efficiency of the turbine.