Flow and heat transfer in swirl tubes — A review

The development of modern gas turbines for aircraft propulsion and power generation demands ever-increasing efficiency, which can be achieved by rising the turbine inlet temperature. Therefore, turbine components and especially the leading edge of turbine blades are exposed to particular high thermal loads with temperatures that are well above the melting point of the material. As a result, efficient cooling techniques are essential. Swirling flows in cyclone cooling systems are a promising technique for internal turbine blade leading edge cooling since they promise high heat transfer rates in combination with relatively uniform heat transfer distributions. The current paper presents a review on cyclone cooling with detailed evaluation of the flow field and heat transfer. Content is focussed on the analysis of basic physical processes and on comparisons of specific design features of swirl tubes. A large data set was collected from literature that allows to elucidate the cooling performance of such systems in comparison to other traditional techniques. Additionally, the numerical predictability of different turbulence modeling approaches is assessed. The review concludes with a summary on open questions that require attention in future cyclone cooling research.