Proceedings of ASME Turbo Expo 2009: Power for Land, Sea and Air GT2009 June 8-12, 2009, Orlando, Florida, USA GT2009-59171 EXPERIMENTAL ANALYSIS OF THE COMBUSTION BEHAVIOR OF A GAS TURBINE BURNER BY LASER MEASUREMENT TECHNIQUES Holger Ax * , Ulrich Stopper, Wolfgang Meier, Manfred Aigner German Aerospace Center (DLR) Institute of Combustion Technology Pfaffenwaldring 38-40, D-70563 Stuttgart, Germany Email: holger.ax@dlr.de Felix G ¨ uthe ALSTOM (Switzerland) Ltd. ABSTRACT Experimental results from optical and laser spectroscopic measurements on a scaled industrial gas turbine (GT) burner at elevated pressure are presented. Planar laser induced ﬂuorescence on the OH radical and OH* chemiluminescence imaging were applied to natural gas/air ﬂames for a qualitative analysis of the position and shape of the ﬂame brush, the ﬂame front and the stabilization mechanism. The results exhibit two different ways of ﬂame stabilization, a conical more stable ﬂame and a pulsating opened ﬂame. For quantitative results, 1D-laser Raman scattering was applied to these ﬂames and evaluated on an average and single shot basis in order to simultaneously determine the major species concentrations, the mixture fraction and the temperature. The mixing of fuel and air as well as the reaction progress could thus be spatially and temporally resolved, showing differently strong variations depending on the ﬂame stabilization mode and the location in the ﬂame. [Keywords: laser diagnostics, Raman scattering, gas turbine combustor, ﬂame stabilization] INTRODUCTION The lean premixed combustion concept is widely applied in stationary gas turbines (GT) in order to achieve low NOx levels. However, these ﬂames are prone to combustion instabilities in the form of unsteady ﬂame stabilization or thermoacoustic pul- sations [1–5]. These phenomena arise from a complex interac- * Address all correspondence to this author. tion between the turbulent ﬂow ﬁeld, the ﬂame reactions and the combustor geometry. Further, effects of unmixedness have a sig- niﬁcant inﬂuence on the ﬂame stabilization and emissions [6, 7]. Different approaches have been reported to reduce or even elim- inate the unsteady effects, e.g. active or passive control mecha- nisms [8–13] or fuel staging [14]. However, a fundamental un- derstanding of the underlying mechanisms has not been reached so far and further experimental and numerical studies are nec- essary before the potential of lean premixed combustion can be fully exploited. In recent years, detailed laser diagnostic studies in GT- relevant combustors have contributed signiﬁcantly to a better un- derstanding of processes like ﬂame stabilization, combustion in- stabilities, pollutant formation and ﬁnite-rate chemistry effects. Frequently used measuring techniques were particle image ve- locimetry (PIV) or laser Doppler velocimetry (LDV) for the ﬂow ﬁeld, laser induced ﬂuorescence (LIF) for ﬂame radicals, tracers, pollutants or temperature, coherent anti-Stokes Raman scattering (CARS) for temperature, and laser Raman scattering for species concentrations. Overviews and detailed descriptions of the dif- ferent laser measurement techniques can be found in [15–18]. In some research groups, high-pressure test rigs have been equipped with optical access in order to apply these techniques to GT com- bustion processes under realistic conditions, i.e. preheated air, elevated pressure, high thermal loads, high turbulence levels and relevant combustor geometries, see for example [19–28]. In the investigations presented here, a scaled industrial GT burner was installed in the high pressure test rig at the Insti- tute of Combustion Technology of the German Aerospace Cen- 1 Copyright c  2009 by ASME