Within the framework of the German collaborative research centre "SFB1029", dynamically forced impingement cooling is investigated experimentally. This will provide a contribution to compensate the critical effects of a turbine inlet temperature increase induced by innovative combustion concepts. The present study describes experimental investigations regarding dynamically forced heat transfer between a flat hot surface and an array of up to 7 by 7 circular impingement jets. Fast switching solenoid valves are used to periodically pulse each cooling jet separately by changing frequency, duty cycle and phasing. Depending on the excitation parameters, strong ring vortices can be generated around each single jet. Thereby the maximum velocity within the core zone of each single jet can be significantly increased. Simultaneously, the vorticity is increased, which induces higher local and temporal wall shear stress after impinging on the wall and thus enhanced forced convective heat transfer as well. Considering a multi nozzle arrangement, the vortex structures of each impingement jet will interfere with the adjacent ones, which strongly influences cooling effectiveness.
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