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

发展工业燃气轮机和航空燃气轮机的主要目标是减少燃料消耗以及大幅减少污染物排放。这可以例如通过借助于过程温度的升高来提高燃气涡轮机的热效率来实现。然而，增加的燃烧室温度和增加的涡轮机入口温度如今已经远高于叶片材料的熔化温度，这使得有必要开发有效的涡轮机叶片内部冷却策略。目前，各种内部冷却的概念正在详细研究，如肋通道，针翅，冲击射流，酒窝和旋风冷却室。旋风冷却（旋流冷却或涡流管）的特点是传热率非常高。在该项目的第一个资助期（FP1），涡流管与收敛管截面的流动方向进行了研究实验和数值模拟。在这里，可以实现测量结果之间的非常好的协议，例如用瞬态液晶技术和分离延迟涡模拟（DDES）测量的传热。此外，稳定性效应在传热和传质过程中起着重要作用。因此，涡流管中的流动的稳定性进行了研究，使用各种稳定性标准，重点是稳定性标准的Marsik，这是基于热力学第二定律。在第二个资助期（FP2）的当前提案中，研究现在将扩展到在主流方向上具有发散横截面的旋风冷却室。由于在流动方向上变宽的横截面积，涡流和所产生的分离面积受到显著影响。因此，以有针对性的方式使流动不稳定。预计成形将导致更高的传热速率。类似于FP1，发散型旋风冷却室中的流动和传热将通过DDES进行数值研究，并通过PIV和瞬态液晶方法进行实验研究。此外，这种几何形状的稳定性研究将再次进行热力学第二定律的基础上。 六年后，在项目结束时，将详细了解旋流冷却室中收敛和发散横截面流的影响。对收敛和发散涡流管中非常复杂的流动和热传递的这种理解应有助于将来成功地将这种冷却系统用于叶片冷却，例如用于新型燃气涡轮机叶片。

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.