Experimental and numerical investigation of the flow and heat transfer in conical Swirl Cooling Chambers

工业燃气轮机和航空燃气轮机发展的主要目标是降低燃料消耗和大幅减少污染物排放。这可以通过例如通过提高工艺温度来提高燃气轮机的热效率来实现。然而，燃烧室温度的提高和涡轮进口温度的提高今天已经远远高于叶片材料的熔化温度，这使得有必要开发高效的涡轮叶片内部冷却策略。目前，各种内部冷却概念正在被详细研究，如肋形通道、销钉、冲击射流、凹坑和旋风冷却室。旋风冷却(旋流冷却或涡流管)具有非常高的传热率。在本项目的第一个资助期(FP1)，对流动方向上具有收敛管截面的涡管进行了实验和数值研究。在这里，用瞬变液晶技术测量的热传递与分离的延迟涡模拟(DDES)之间的测量结果可以达到很好的一致性。此外，稳定性效应在传热传质过程中起着重要的作用。为此，采用各种稳定性判据对涡流管内流动的稳定性进行了研究，其中重点研究了Marsik基于热力学第二定律的稳定性判据。在目前关于第二个资金期的提案(第二阶段)中，现在将调查范围扩大到在主要流动方向上具有分叉截面的旋风冷却室。由于水流方向的横截面积变宽，漩涡和由此产生的脱落区受到显著影响。因此，这种流动以一种有针对性的方式破坏了稳定。预计成型将导致更高的换热速率。类似于FP1，我们将用数值模拟的方法研究扩散式旋风冷却室内的流动和换热，并用PIV和瞬变液晶法进行实验研究。此外，这种几何形状的稳定性研究将再次基于热力学第二定律进行。在项目结束时，在六年后，将有关于旋流冷却室内收敛和发散横截面流动的影响的详细知识。这种对收敛和扩张涡流管内非常复杂的流动和换热的了解，应该有助于在未来成功地将这种冷却系统用于叶片冷却，例如在新型燃气轮机叶片中。

The main goals in the development of industrial gas turbines and aero-gas turbines are the reduction of fuel consumption as well as the drastic reduction of pollutant emissions. This can be achieved, for example, by increasing the thermal efficiency of the gas turbine with the help of an increase in the process temperature. However, the increased combustion chamber temperature and the increased turbine inlet temperature are today already well above the melting temperature of the blade material, which makes it necessary to develop efficient turbine blade internal cooling strategies. Currently, various internal cooling concepts are being investigated in detail, such as ribbed channels, pin fins, impingement jets, dimples and cyclone cooling chambers. Cyclone cooling (swirl cooling or vortex tubes) are characterized by very high heat transfer rates. In the first funding period (FP1) of this project, vortex tubes with convergent tube cross-sections in the flow direction were investigated both experimentally and numerically. Here, a very good agreement between measurement results, such as the heat transfer measured with the transient liquid crystal technique and Detached Delayed Eddy Simulations (DDES) could be achieved. In addition, stability effects play an important role in heat and mass transfer processes. Therefore, the stability of the flow in the vortex tube was investigated using various stability criteria, with a focus on the stability criterion by Marsik, which is based on the second law of thermodynamics. In the current proposal for the second funding period (FP2), the investigations are now to be extended to cyclone cooling chambers with diverging cross-sections in the main flow direction. Due to the widening cross-sectional area in the direction of the flow, the swirl and the resulting detachment areas are significantly influenced. The flow is, thus, destabilized in a targeted manner. It is expected that the shaping will lead to higher heat transfer rates. Analogous to FP1, the flow and the heat transfer in the divergent cyclone cooling chambers will be investigated numerically by means of DDES and experimentally by means of PIV and the transient liquid crystal method. Furthermore, stability investigations for this geometry will again be carried out based on the second law of thermodynamics. At the end of the project, after six years, there will be detailed knowledge about the influence of convergent and divergent cross-sectional flows in swirl cooling chambers. This understanding of the very complex flow and heat transfer in convergent and divergent vortex tubes should help to successfully use such cooling systems for blade cooling in the future, for example in new types of gas turbine blades.