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The influence of selected single-component hydrocarbons on lean blowout behavior of swirl-stabilized spray flames was investigated. Additional information on the spray characteristics was collected by Phase Doppler Interferometry (PDI) and Mie scattering measurements. The measurements were accomplished in a gas turbine model combustor under atmospheric pressure and at two different air preheat temperatures.The combustor featured a dual-swirl geometry and a prefilming airblast atomizer. The combustion chamber provided good optical access and yielded well-defined boundary conditions. Three single-component hydrocarbons were chosen: one short and one long linear alkane (n-hexane and n-dodecane) and one branched alkane (iso-octane).Kerosene Jet A-1 was used as a reference. Results show noticeable differences in the lean blowout limits of the various fuels, at comparable flow conditions. By using the results of the measurements, of additional modelling and of an assessment of the fuel properties it was concluded that fuel differences in lean blowout in this combustor can be due to differences in the physical properties as well as in the chemical properties. \phi = global equivalence ratio (-) P th = thermal power (W) \rho = density ( \mathrm{ \mathrm{ /\mathrm{ 3 ) Re = Reynolds number (-) \sigma = surface tension ( \mathrm{ /\mathrm{ ) S = geometrical swirl number (-) t e = total evaporation time (s) T = temperature (K) u, v, w = velocities in reference coordinate system ( \mathrm{ /\mathrm{ ) x, y, z = reference coordinate system (m) I. IntroductionProduction pathways for alternative aviation fuels offer the possibility to modify the chemical composition of the final product in order to improve physical and chemical properties for optimized combustion performance. Depending on feedstock (e.g. coal, natural gas or biomass) and process parameters, alternative fuels can contain hydrocarbons of significantly different types and chain lengths [1,2]. However, the influence of the chemical composition of the fuel on combustion performance is not fully understood [3].Four main processes govern the combustion of liquid fuels in gas turbine combustors: atomization, vaporization, turbulent mixing and chemical reaction. These processes happen simultane-

Alternative production pathways for liquid fuels provide the opportunity to adjust the chemical composition of the product in order to improve combustion performance. In this study, flame characteristics of selected single-component fuels were investigated to provide a basis for a better understanding of the influence of specific fuel components on the combustion behaviour. The measurements were performed in a redesigned gas turbine model combustor for swirl-stabilised spray flames under atmospheric pressure. The combustor features a dual-swirl geometry and a prefilming airblast atomiser. The combustion chamber provides good optical access and yields well-defined boundary conditions. As part of different projects in the field of alternative fuels, two liquid single-component fuels (n-hexane, n-dodecane) and kerosene Jet A-1 were investigated. Flow fields of the nonreacting and reacting flow were measured using stereo particle image velocimetry. The flame structure and spray distribution were derived from CH* chemiluminescence and Mie scattering respectively. Lean blowout limits were measured. Results show noticeable differences in combustion behaviour of the chosen fuels at comparable flow conditions. Furthermore, the results provide a detailed data base for the validation of numerical models.

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Alternative liquid fuels can contain hydrocarbons of different types and chain lengths and the fuel composition has an influence on combustion behavior. In this study, the influence of liquid single-component fuels on exhaust gas emissions of a gas turbine model combustor for swirl-stabilized spray flames was investigated under atmospheric pressure. The nozzle exhibited a dual-swirl geometry and a prefilming airblast atomizer. The spray was characterized by Phase Doppler Anemometry (PDA) and Mie scattering measurements and the flame CH* chemiluminescence was measured. Six single-component hydrocarbons were chosen: three linear alkanes (n-hexane, n-nonane, n-dodecane), one cyclic alkane (cyclohexane), one branched alkane (iso-octane) and one aromatic hydrocarbon (toluene). Kerosene Jet A-1 was used as a technical reference. Results show minor differences in CO emissions and significant differences in NOx emissions of the various fuels at comparable flow conditions and adiabatic flame temperatures. The measurements indicate a correlation between the nitric oxide emissions and the spray quality.

Der vorliegende Beitrag stellt Arbeiten vor, die im Rahmen der dreijährigen Helmholtz‐Energieallianz Synthetische flüssige Kohlenwasserstoffe (SynKWS) – Speicher mit höchster Energiedichte durchgeführt wurden. Unter Einbezug technischer, prozessoptimierender und systemanalytischer Aspekte wurden ausgewählte Pfade für die Erzeugung von flüssigen, synthetischen Kohlenwasserstoffen aus erneuerbaren Energien und Biomassen untersucht und bewertet. Ergänzend erfolgte eine systemanalytische Bewertung synthetischer flüssiger Kohlenwasserstoffe in einem Energiesystem der Zukunft mit hohem Anteil erneuerbarer Energien.

A gas turbine model combustor for swirling spray flames has been operated at atmospheric pressure with n-hexane, n-dodecane and kerosene Jet A-1. Temperature measurements were performed using single-shot broadband shifted vibrational coherent anti-Stokes Raman spectroscopy (SV-CARS). Series of 1200 single-shot measurements were performed at different radial and vertical locations in the flames from which the temperature distributions were deduced. In regions with high droplet load a significant number of CARS spectra were discarded due to large signal background from laser-induced breakdown effects. Results from the flames burning different fuels were compared and revealed considerable differences in the temperature profiles. The temperature measurements are part of a comprehensive research program that aims at the design of alternative fuels for aero engines and stationary gas turbines. In addition to the experimental characterization of the spray flames, the datasets are used for the validation and improvement of computational models.