Influence of Single-Component Fuels on Gas-Turbine Model Combustor Lean Blowout

Abstract

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-

Near-lean blowoff dynamics in a liquid fueled combustor

“…In addition to chemistry and mixing effects, blowoff is also influenced by atomization and vaporization processes. Available data often generate conflicting or inconclusive results [8][9][10][11][12][13][14][15], likely due to the range of potentially dominant physical processes depending upon atomization quality, air preheat temperature, etc. Early approaches to this problem involved generalizing methods developed from premixed combustors.…”

Assessment of the Comparability of Droplet Evaporation Fuel Sensitivities between a Unit Test Case and an Aviation Gas Turbine Combustor

“…To investigate in detail the influence of different fuels (e.g. Jet A-1, Fischer-Tropsch Fuels) on the combustor performance, generic experiments have been successfully developed and used ( [5][6][7]). Furthermore, for the development of fuel-dependent models, unit test experiments have been beneficially used (e.g.…”

Flame Extinction and Re-Ignition in a Swirl Stabilized Prevaporized Liquid Fuel Flame Close to Lean Blow-Out

“…Here, prevaporized liquid fuels have the potential to separate physical and chemical processes, allowing studying the combustion properties of different fuels based on their chemical properties alone. One important aspect is the lean blow-out (LBO) limit of different fuels [7][8][9] and hence also the dynamics of the lean blow-out process [10][11][12]. Since this process is highly dynamic and occurs on timescales on the order of milliseconds, optical diagnostics with high spatio-temporal resolution are necessary in order to fully resolve this phenomenon.…”