Laser-based investigations in gas turbine model combustors |
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Authors: | W Meier I Boxx M Stöhr C D Carter |
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Institution: | 1. Institut für Verbrennungstechnik, Deutsches Zentrum für Luft- und Raumfahrt (DLR), Pfaffenwaldring 38, 70569, Stuttgart, Germany 2. Air Force Research Laboratory, Wright-Patterson Air Force Base, Dayton, OH, 45433, USA
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Abstract: | Dynamic processes in gas turbine (GT) combustors play a key role in flame stabilization and extinction, combustion instabilities
and pollutant formation, and present a challenge for experimental as well as numerical investigations. These phenomena were
investigated in two gas turbine model combustors for premixed and partially premixed CH4/air swirl flames at atmospheric pressure. Optical access through large quartz windows enabled the application of laser Raman
scattering, planar laser-induced fluorescence (PLIF) of OH, particle image velocimetry (PIV) at repetition rates up to 10 kHz
and the simultaneous application of OH PLIF and PIV at a repetition rate of 5 kHz. Effects of unmixedness and reaction progress
in lean premixed GT flames were revealed and quantified by Raman scattering. In a thermo-acoustically unstable flame, the
cyclic variation in mixture fraction and its role for the feedback mechanism of the instability are addressed. In a partially
premixed oscillating swirl flame, the cyclic variations of the heat release and the flow field were characterized by chemiluminescence
imaging and PIV, respectively. Using phase-correlated Raman scattering measurements, significant phase-dependent variations
of the mixture fraction and fuel distributions were revealed. The flame structures and the shape of the reaction zones were
visualized by planar imaging of OH distribution. The simultaneous OH PLIF/PIV high-speed measurements revealed the time history
of the flow field–flame interaction and demonstrated the development of a local flame extinction event. Further, the influence
of a precessing vortex core on the flame topology and its dynamics is discussed. |
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