Combustion and Flame 144 (2006) 205–224 www.elsevier.com/locate/combustﬂame Investigations of swirl ﬂames in a gas turbine model combustor I. Flow ﬁeld, structures, temperature, and species distributions P. Weigand, W. Meier ∗ , X.R. Duan 1 , W. Stricker, M. Aigner Institut für Verbrennungstechnik, Deutsches Zentrum für Luft- und Raumfahrt (DLR), Pfaffenwaldring 38, D-70569 Stuttgart, Germany Received 22 November 2004; received in revised form 2 June 2005; accepted 8 July 2005 Available online 21 September 2005 Abstract A gas turbine model combustor for swirling CH 4 /air diffusion ﬂames at atmospheric pressure with good optical access for detailed laser measurements is discussed. Three ﬂames with thermal powers between 7.6 and 34.9 kW and overall equivalence ratios between 0.55 and 0.75 were investigated. These behave differently with respect to combustion instabilities: Flame A burned stably, ﬂame B exhibited pronounced thermoacoustic oscillations, and ﬂame C, operated near the lean extinction limit, was subject to sudden liftoff with partial extinction and reanchor- ing. One aim of the studies was a detailed experimental characterization of ﬂame behavior to better understand the underlying physical and chemical processes leading to instabilities. The second goal of the work was the estab- lishment of a comprehensive database that can be used for validation and improvement of numerical combustion models. The ﬂow ﬁeld was measured by laser Doppler velocimetry, the ﬂame structures were visualized by planar laser-induced ﬂuorescence (PLIF) of OH and CH radicals, and the major species concentrations, temperature, and mixture fraction were determined by laser Raman scattering. The ﬂow ﬁelds of the three ﬂames were quite sim- ilar, with high velocities in the region of the injected gases, a pronounced inner recirculation zone, and an outer recirculation zone with low velocities. The ﬂames were not attached to the fuel nozzle and thus were partially pre- mixed before ignition. The near ﬁeld of the ﬂames was characterized by fast mixing and considerable ﬁnite-rate chemistry effects. CH PLIF images revealed that the reaction zones were thin (0.5 mm) and strongly corrugated and that the ﬂame zones were short (h  50 mm). Despite the similar ﬂow ﬁelds of the three ﬂames, the oscillating ﬂame B was ﬂatter and opened more widely than the others. In the current article, the ﬂow ﬁeld, structures, and mean and rms values of the temperature, mixture fraction, and species concentrations are discussed. Turbulence intensities, mixing, heat release, and reaction progress are addressed. In a second article, the turbulence–chemistry interactions in the three ﬂames are treated.  2005 The Combustion Institute. Published by Elsevier Inc. All rights reserved. * Corresponding author. Fax: +49 711 6862 578. E-mail address: wolfgang.meier@dlr.de (W. Meier). 1 Present address: Southwestern Institute of Physics, P.O. Box 432, 610041 Chengdu Sichuan, People’s Republic of China. 0010-2180/$ – see front matter  2005 The Combustion Institute. Published by Elsevier Inc. All rights reserved. doi:10.1016/j.combustﬂame.2005.07.010