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International audience; Research on the production and combustion of synthetic jet fuels has recently gained importance because of their potential for addressing security of supply and sustainable air transportation challenges. The combustion of a 100% naphtenic cut that fits with typical chemical composition of products coming from biomass or coal liquefaction (C12.64H23.64; M=175.32 g.mol-1; H/C=1.87; DCN=39; density=863.1 g.L-1) and a 50% vol. mixture with Gas to Liquid from Shell (mixture: C11.54H23.35; M=161.83 g.mol-1; H/C=2.02; DCN=46; density=800.3 g.L-1) were studied in a jet-stirred reactor under the same conditions (temperature, 550-1150 K; pressure, 10 bar; equivalence ratio, 0.5, 1, and 2; initial fuel concentration, 1000 ppm). Surrogate model-fuels were designed based on fuel composition and properties for simulating the kinetics of oxidation of these fuels. We used new model-fuels consisting of mixtures of n-decane, decalin, tetralin, 2-methylheptane, 3-methylheptane, n-propyl cyclohexane, and n-propylbenzene. The detailed chemical kinetic reaction mechanism proposed was validated using the entire experimental database obtained in the present work and for the oxidation of pure GtL, we used previous results. Kinetic computations involving reaction paths analyses and sensitivity analyses were used to interpret the results.

During the last years, the aviation sector has been looking into alternatives to kerosene from crude oil, to combat climate change by reduction of greenhouse gas (GHG) emissions and to ensure security of supply at affordable prices. The efforts are also a reaction to commitments and policy packages. Currently, a wide range of possible fuel candidates and fuel blends are discussed in the triple feedstock, process, and product. Any (synthetic) aviation fuel must be certified; hence, a profound knowledge on its properties, in particular thermophysical and chemical, is inevitable. In the present paper, an overview is given on alternative jet fuels, looking into the short-term and long-term perspective. Examples focusing on experimental and modeling work of combustion properties of existing—coal to liquid, gas to liquid (GtL)—and possible alternative fuels—GtL + 20 % 1-hexanol, GtL + 50 % naphthenic cut—are presented. Ignition delay times and laminar flame speeds were measured for different alternative aviation fuels over a range of temperatures, pressures, and fuel–air ratios. The data are used for the validation of a detailed chemical reaction mechanism following the concept of a surrogate. Such validated reaction models able to describe and to predict reliably important combustion properties of jet fuels are needed to further promote the development of even more sophisticated jet engines and to optimize synthetic jet fuel mixtures in practical combustors.

<p>This paper – in memory of Jürgen Warnatz – summarizes selected recent papers of the Chemical Kinetics Group at the German Aerospace Center in Stuttgart. It shows the need for detailed chemical reaction mechanisms to understand practical combustion systems. A comprehensive description of combustion processes based on detailed mechanisms is especially important in the design of new gas turbine combustion chambers and in the optimization of existing ones to improve efficiency and to reduce pollutant emissions, with fuel-flexibility and load-flexibility ever becoming more important. Different aspects of combustion processes where detailed reaction mechanisms provide useful insights will be covered in this paper: Fuels (alternative jet fuels, biomass based fuels), pollutants (soot), diagnostics (chemiluminescence), and thermochemistry. Furthermore, the underlying thermodynamics inevitably connected with detailed reaction schemes will be addressed. Exemplified results will be presented clearly demonstrating the predictive capabilities of detailed reaction mechanisms to be explored in computational fluid dynamic simulations to further optimize technical combustion systems.</p>

Abstract The kinetics of oxidation, ignition, and combustion of Gas-to-Liquid (GtL) Fischer–Tropsch Synthetic kerosene as well as of a selected GtL-surrogate were studied. New experimental results were obtained using (i) a jet-stirred reactor – species profiles (10 bar, constant mean residence time of 1 s, temperature range 550–1150 K, equivalence ratios φ = 0.5, 1, and 2), (ii) a shock tube – ignition delay time (≈16 bar, temperature range 650–1400 K, φ = 0.5 and 1), and (iii) a burner – laminar burning velocity (atmospheric pressure, preheating temperature = 473 K, 1.0 ⩽ φ ⩽ 1.5). The concentrations of the reactants, stable intermediates, and final products were measured as a function of temperature in the jet-stirred reactor (JSR) using probe sampling followed by on-line Fourier Transformed Infra-Red spectrometry, and gas chromatography analyses (on-line and off-line). Ignition delay times behind reflected shock waves were determined by measuring time-dependent CH* emission at 431 nm. Laminar flame speeds were obtained in a bunsen-type burner by applying the cone angle method. Comparison with the corresponding results for Jet A-1 showed comparable combustion properties. The GtL-fuel oxidation was modeled under these conditions using a detailed chemical kinetic reaction mechanism (8217 reactions vs. 2185 species) and a 3-component model fuel mixture composed of n-decane, iso-octane (2,2,4-trimethyl pentane), and n-propylcyclohexane. The model showed good agreement with concentration profiles obtained in a JSR at 10 bar. In the high temperature regime, the model represents well the ignition delay times for the fuel air mixtures investigated; however, the calculated delays are longer than the measurements. It was observed that the ignition behavior of the surrogate fuel is mainly influenced by n-alkanes and not by the addition of iso-alkanes and cyclo-alkanes. The simulated laminar burning velocities were found in excellent agreement with the measurements. No deviation between burning velocity data for the GtL-surrogate and GtL was seen, within the uncertainty range. The presented data on ignition delay times and burning velocities agree with earlier results obtained for petrol-derived jet fuel. The suitability of both the current detailed reaction model and the selected GtL surrogate was demonstrated. Finally, our results support the use of the GtL fuel as an alternative jet fuel.

The kinetics of oxidation of a Coal-to-Liquid (CtL) Fully Synthetic Jet Fuel (FSJF) was studied using three complementary experiments operating over a wide range of conditions: a jet stirred reactor (p = 10 bar), constant mean residence time of 1 s, over the temperature range 570–1070 K, and for equivalence ratios φ = 0.5, 1.0, and 2.0; a shock-tube (p ∼ 16 bar, temperature range between 900 and 1400 K, φ = 0.5 and φ = 1), and a conical flame burner (preheat temperature T0 = 473 K, and for two pressure regimes, p = 1 bar for equivalence ratios ranging from 0.95 to 1.4, and p = 3 bar for equivalence ratios ranging from 0.95 to 1.3). Concentration profiles of reactants, stable intermediates, and final products in the jet stirred reactor were obtained by probe sampling followed by online and off-line gas chromatography analyses and online Fourier transform infrared spectrometry. Ignition delay times were determined behind reflected shock waves by measuring time-dependent CH* emission at 431 nm. Flame speeds ...

Abstract Recently, the development of viable alternative aviation fuels has attracted much interest, for several reasons, with reduction of greenhouse gas (GHG) emissions and ensuring security of supply at affordable prices among them. In the present work, several alternative aviation fuels - existing and potential - are investigated by focusing on their heat release: Gas-to-Liquid (GtL: representing a Fischer-Tropsch Synthetic Paraffinic Kerosene (FT-SPK)), a fully synthetic jet fuel (FSJF: Coal-to-Liquid (CtL)), and blends of GtL with 20% 1-hexanol or 50% naphthenic cut, respectively. Burning velocities are measured at ambient pressures and at elevated preheat temperatures exploiting the cone-angle method; equivalence ratios are between about ϕ = 1.0 and ϕ = 1.4. The measured data are used for the validation of a detailed chemical reaction model consisting of 4642 reactions involving 1075 species developed by Dagaut et al. [22] , [23] following the concept of a surrogate. The comparison between measured burning velocities and predicted laminar flame speeds shows reasonably good agreement with the model for the range of conditions considered in this study. The main features of the reaction model are also discussed, using sensitivity and rate of production analysis. Finally, the experimental data are compared with results obtained earlier for crude-oil kerosene. The findings support the potential of the investigated fuel mixtures to serve as alternative aviation fuels.

The use of alternative and renewable energy resources is in the focus of numerous investigations, to meet challenges such as reduction of greenhouse gas (GHG) emissions and ensuring security of supply at affordable prices. The aviation sector is embedded in the EU policy package although jet fuels constitute presently only about 4¬6 percent to the global crude oil consumption. In 2011, the European Commission has launched the European Advanced Biofuels Flight Path, an industry wide initiative to speed up the commercialization of aviation biofuels in Europe. The development of viable alternative aviation fuels has spurred many research activities. A profound knowledge on jet fuels properties is inevitable, in particular thermophysical and chemical properties, due to the aircraft's needs. Any (synthetic) aviation fuel must be characterized and certified. Furthermore, validated reaction models must be elaborated, which are able to describe and to predict reliably important combustion properties of alternative aviation fuels, to further promote the development of even more sophisticated jet engines. In the present article, an overview is given on the status quo of alternative jet fuels. In addition, some results on investigations of major combustion properties of reformulated kerosenes (FSJF, FT-SPK, FT-SPK+20% 1-hexanol, FT-SPK+50% naphthenic cut) performed within the framework of ALFA-BIRD will be presented. The predictive capability of the detailed reaction mechanism used in simulations will be discussed. Proceedings of the 20th European Biomass Conference and Exhibition, 18-22 June 2012, Milan, Italy, pp. 1547-1554

Abstract Background Yarrowia lipolytica is an oleaginous yeast which has emerged as an important microorganism for several biotechnological processes, such as the production of organic acids, lipases and proteases. It is also considered a good candidate for single-cell oil production. Although some of its metabolic pathways are well studied, its metabolic engineering is hindered by the lack of a genome-scale model that integrates the current knowledge about its metabolism. Results Combining in silico tools and expert manual curation, we have produced an accurate genome-scale metabolic model for Y. lipolytica. Using a scaffold derived from a functional metabolic model of the well-studied but phylogenetically distant yeast S. cerevisiae, we mapped conserved reactions, rewrote gene associations, added species-specific reactions and inserted specialized copies of scaffold reactions to account for species-specific expansion of protein families. We used physiological measures obtained under lab conditions to validate our predictions. Conclusions Y. lipolytica iNL895 represents the first well-annotated metabolic model of an oleaginous yeast, providing a base for future metabolic improvement, and a starting point for the metabolic reconstruction of other species in the Yarrowia clade and other oleaginous yeasts.

This article analyses energy efficiency coefficients and their evolution in the air transport sector. The proposed ’macro-level’ methodology allows obtaining energy efficiency coefficients and their growth rates (corresponding to the evolution of energy gains) from 1983 to 2006 for eight distinct geographical regions and at the world level. During the whole period, energy efficiency improvements have been equal to 2.88% per year at the world level, with strong differences between regions. Moreover, our results indicate that domestic air travels are less energy efficient (i.e. more carbon intensive) than international air travels. This result applies in all regions.; La collection "Les cahiers de l'économie" a pour objectif de présenter des travaux réalisés à IFP Energies nouvelles et à IFP School, travaux de recherche ou notes de synthèse en économie, finance et gestion. La forme peut être encore provisoire, afin de susciter des échanges de points de vue sur les sujets abordés. Les opinions émises dans les textes publiés dans cette collection doivent être considérées comme propres à leurs auteurs et ne reflètent pas nécessairement le point de vue d' IFP Energies nouvelles ou d' IFP School. Pour toute information sur le contenu, prière de contacter directement l'auteur. Pour toute information complémentaire, prière de contacter le Centre Économie et Gestion: Tél +33 1 47 52 72 27

An experimental study is conducted for the laminar, atmospheric pressure, sooting, coflow diffusion flames of prevaporized Jet A-1 and four synthetic jet fuels to compare their sooting characteristics and flame structures. Soot volume fraction, species concentration, and temperature profiles are measured, using the laser extinction measurement method, gas chromatography, and fine wire thermocouples, respectively. To evaluate the sooting tendency of the fuels, their smoke point heights are measured using the ASTM D1322 method and compared. The synthetic jet fuels under investigation are (1) Fully Synthetic Jet Fuel (FSJF), which is a coal-to-liquids (CtL) kerosene plus some coal tar derived material from Sasol, (2) Fischer–Tropsch Synthetic Paraffinic Kerosene (FT-SPK), which is a gas-to-liquids (GtL) product from Shell, (3) SPK plus naphthenic cut (50% by volume), and (4) SPK plus hexanol (20% by volume). The threshold sooting index (TSI) of the proposed surrogate mixtures for the fuels are calculated and...