02.09.2011 - 13:56:13

Vortragsankündigung

06. September 2011 um 14 Uhr - Isaac Box

Vortragender: Isaac Box
Deutsches Zentrum für Luft- und Raumfahrt e.V.
Institut für Verbrennungstechnik, Stuttgart
Thema: A technique to visualize the out-of-plane flame sheet in highspeed PIV / PLIF measurements
Uhrzeit: 14 Uhr
Raum: MB 144

Abstract:
Recently developed planar imaging diagnostics with kHz-acquisition rates and measurement periods of a second or more provide an excellent source of validation data for time-dependent combustion simulation techniques such as URANS and LES. The simultaneous application of particle image velocity (PIV) and planar laser-induced fluorescence (PLIF) of a combustion radical such as hydroxyl (OH) enable one to track specific flow-field/flame interactions as they occur and to spatiotemporally condition statistics on the physical phenomena under study. They provide a means to identify and track transient or unpredictable phenomena such as flame dynamics linked to thermo-acoustic pulsation, local extinction and re-ignition of a flame sheet and blow-off or flashback events previously obscured by the need to average temporally uncorrelated planar measurements. Unfortunately, the phenomena under study frequently depend strongly on the state of the flame-sheet beyond the plane of imaging, which remains inaccessible. The lack of direct experimental access to the flame sheet beyond the plane of imaging complicates the interpretation of planar measurements considerably and makes definitive answers to certain fundamental questions virtually impossible.

In this talk an innovative flow-visualization diagnostic technique developed at the German Aerospace Center (DLR) designed to help contextualize planar measurements by simultaneously acquiring line-of-sight integrated OH* chemiluminescence (OH* CL) and OH-PLIF on a single camera will be presented. The technique is applied to the study of a series of lifted turbulent jet-flames, and the results compared with conventional high-speed OH-PLIF measurements acquired simultaneously. Results indicate that circumferential flame propagation and flamebase wrinkling are dominant effects in the stabilization region of such flames but this fact is badly obscured by the limitation of PIV/PLIF measurements to a single imaging plane.