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MAGNETIC RESONANCE VELOCIMETRY IN COMPLEX TURBULENT INTERNAL FLOWS

Christopher J. Elkins
Department of Mechanical Engineering Stanford University 488 Escondido Mall Stanford, California 94305

John K. Eaton
Dept. of Mechanical Engineering Stanford University 488 Panama Mall Stanford, CA 94305 USA

Michael Markl
Department of Radiology, Lucas MRI/S Genter Stanford, California 94305-5105, USA

Norbert Pelc
Department of Radiology, Lucas MRI/S Genter Stanford, California 94305-5105, USA

Resumo

The aim of this paper is to apply a technique called 4D magnetic resonance velocimetry (4D-MRV) to measure the mean flow in a model of a gas turbine blade internal cooling geometry with four serpentine passages for three different Reynolds numbers (10,000, 21,000, and 53,000) based on bulk mean velocity and hydraulic diameter. The Reynolds number effects in this flow are also investigated. 4D-MRV utilizes an adaptation of a medical magnetic resonance imaging system to noninvasively measure the three component mean velocity field in complex turbulent flows. 4D-MRV is capable of completing full field measurements in three-dimensional volumes with sizes on the order of the magnet bore diameter in less than 1 hour. Such measurements can include over 2 million independent mean velocity vectors. In the turbulent passage flow, the average flow rates calculated from the 4D-MRV velocity profiles agreed with flow measurements to within 4%. The measurements lend excellent qualitative insight into flow structures even in the highly complex 180° bends. Accurate quantitative measurements were obtained throughout the flows for all three Reynolds numbers. While the large features of the flow remain basically the same as the Reynolds number increased, many differences occur as well. In particular, the size of the separation region downstream of the bends and turbulators decreases slightly with increasing Reynolds number. The 4D-MRV measurements provide very detailed three-dimensional data ideal for comparing to CFD.