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Experimental Investigation of a 7 by 7 Nozzle Jet Array for Dynamic Impingement Cooling

Haucke, Frank; Kroll, Henning; Peltzer, Inken; Nitsche, Wolfgang

SFB 1029 - TurbIn

Dynamic impingement cooling is a promising way for more efficient exploitation of cooling air in highly heat charged environments. In many applications the deployed impinging jets are subjected to crossflow superimposed on the flow field of the transverse jets. The present study describes the initial experimental investigations regarding dynamic heat transfer between a flat surface and an array of 49 impingement jets, which are dynamically controlled by changing frequency, duty cycle and phasing. A new test rig was designed and manufactured in order to investigate the interactions of impingement jets and their impact on heat transfer. The test rig satisfies the needs of different measurement techniques. Surface measurements using pressure sensors, thermocouples, hot wires, hot films and liquid crystal thermography are planned for investigating the interactions near the wall. Furthermore, the test rig is suitable for efficient flow field measurements between jet orifices and impingement plate using particle image velocimetry. Parallel to the test rig development, time resolved PIV measurements have been performed in the test section of a recirculating free-surface water tunnel in order to investigate the influence of cross flow superimposed to periodically generated vortex rings impinging on a flat plate. The central goal of these preliminary testing is to understand under which formation conditions periodically generated vortex rings in cross flow have the ability to maximize the transport of vorticity close to the wall. First results are presented and discussed.