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SWIRL FLOW FORMATIONS IN COOLING DUCTS

DOI: 10.1615/ICHMT.2014.IntSympConvHeatMassTransf.840
pages 1123-1144

Martin Bruschewski
Institute of Gas Turbines and Aerospace Propulsion, Technische Universität Darmstadt, 64287 Darmstadt, Germany

Christian Scherhag
Institute of Gas Turbines and Aerospace Propulsion, Technische Universität Darmstadt, 64287 Darmstadt, Germany

Sven Grundmann
Department of Mechanical Engineering Institute of Fluid Mechanics and Aerodynamics (SLA) / Center of Smart Interfaces (CSI) Technische Universitat Darmstadt Petersenstrasse 17, D-64287 Darmstadt, Germany

Heinz-Peter Schiffer
Institute of Gas Turbines and Aerospace Propulsion, Technische Universität Darmstadt, 64287 Darmstadt, Germany

要約

Experimental results on the strongly swirling flow field in a circular pipe are presented. A comprehensive parameter study was conducted in which the sensitivity of the flow to geometric and fluid mechanic parameters was investigated. The swirl system in this study consists of a straight tube of large length-to-diameter ratio with a tangential-type swirl generator at the bottom and an exchangeable outlet at the opposite exit. The study was carried out with the novel measurement technique Magnetic Resonance Velocimetry with deionized water as flow medium. Two robust swirl flow types were identified that tolerate broad changes in geometry and flow conditions. Justified by their great universality and reproducibility they are regarded as natural forms of swirling flow. They are named Stagnant-Core and Forward-Core vortex according to their axial velocity distribution. In the second part of this work, the identified flow formations are discussed with respect to their applicability for heat transfer tasks. Based on the three-dimensional flow field and heat transfer correlations by other studies, it was concluded that the two vortex types are both particularly suitable for the application. However, there are differences which in conclusion proved the Stagnant-Core vortex as the more advantageous type for the purpose of heat transfer enhancement. In addition, the flows were analyzed towards boundary layer instability in form of Goertler vortex pairs. It is shown that Goertler-vortex-like structures are presumably present and that the high heat transfer enhancement could be attributed towards this phenomenon. Due to the extreme robustness of the flow, the findings of this study are transferable to more complex channel geometries such as the multi-pass cooling ducts in turbine blades.

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