Progress in Energy and Combustion Science 32 (2006) 48–92 www.elsevier.com/locate/pecs The ignition, oxidation, and combustion of kerosene: A review of experimental and kinetic modeling Philippe Dagaut *, Michel Cathonnet CNRS, Laboratoire de Combustion et Syste`mes Re´actifs (LCSR), UPR 4211, 1c, Avenue de la recherche scientifique, 45071 Orle´ans Cedex 2, France Received 24 March 2005; accepted 28 October 2005 Abstract For modeling the combustion of aviation fuels, consisting of very complex hydrocarbon mixtures, it is often necessary to use less complex surrogate mixtures. The various surrogates used to represent kerosene and the available kinetic data for the ignition, oxidation, and combustion of kerosene and surrogate mixtures are reviewed. Recent achievements in chemical kinetic modeling of kerosene combustion using model-fuels of variable complexity are also presented. q 2005 Elsevier Ltd. All rights reserved. Keywords: Ignition; Oxidation; Combustion; Kinetics; Kerosene; Surrogate; Modeling Contents 1. Introduction . ....................................................................... 48 2. Characteristic properties of conventional jet fuels ............................................... 49 3. Formulation of kerosene surrogate fuels ...................................................... 50 4. Experimental kinetic studies of the ignition, oxidation and combustion of kerosene and surrogates ........... 57 4.1. Kerosene ....................................................................... 57 4.2. Surrogates ...................................................................... 58 5. Literature survey of the chemical kinetic modeling of the combustion of Jet A-1/JP-8 .................... 71 6. New kinetic modeling of kerosene oxidation and combustion ...................................... 83 7. Reformulated jet-fuels ................................................................... 86 8. Concluding remarks .................................................................... 86 Acknowledgements ..................................................................... 89 Appendix A. ....................................................................... 89 References ........................................................................... 90 1. Introduction Until now, fossil fuels have contributed to over 80% of * Corresponding author. Tel.: C33 238 25 54 66; fax: C33 238 69 energy expenses, and among them, oil played the 60 04. dominant role. It is expected that its use will not decline E-mail address: [email protected] (P. Dagaut). until the next two or three decades. The transportation 0360-1285/$ - see front matter q 2005 Elsevier Ltd. All rights reserved. doi:10.1016/j.pecs.2005.10.003 P. Dagaut, M. Cathonnet / Progress in Energy and Combustion Science 32 (2006) 48–92 49 Nomenclature FID flame ionization detector PRF primary reference fuels (n-heptane and GC gas chromatography iso-octane also called 1,2,4- JSR jet-stirred reactor (also called continu- trimethylpentane) ously stirred tank reactor, CSTR) SI engine spark ignition engine MS mass spectrometry t mean residence time in the jet-stirred Naphtene also called cycloalkane reactor P total pressure T temperature PAH poly-aromatic hydrocarbon TCD thermal conductivity detector ppmv part per million in volume (1 ppmv f equivalence ratio ({[fuel]/[O2]}/{[fuel]/ K6 corresponds to a mol fraction of 1!10 ) [O2]}atstoichiometry; fZ1 at stoichiometry sector, including aviation, an essential part of our modern 2. Characteristic properties of conventional jet fuels society, represents the largest part of the petroleum based fuels consumption. Its importance has continuously Since the early development of the turbojet engine, the grown at a very fast rate over the last century. Future characteristics of jet fuels have evolved [1].Initially,the global energy and environmental issues have imposed turbojet engines were thought to be relatively insensitive changes in the operating conditions of turbojet engines. to fuel properties. Therefore, the widely available As in other sectors, research is now oriented on saving illuminating kerosene produced for wick lamps was energy, in parallel with enhanced protection of our used. In the 1940s, ‘wide-cut’ fuel was used for environment (reduction of the emissions of pollutants and availability reasons. Due to its relative high-volatility green house gases) and fuel reformulation. The detailed and associated evaporation and safety problems, wide-cut modeling of the combustion of jet fuels is a useful tool to jet fuels (JP-4, Jet B) were replaced by kerosene-type fuel solve the problem of combustion control, as well as to in the 1970s (Jet A, Jet A-1, and JP-8). Nowadays, there reduce emissions and fuel consumption. Such a modeling are essentially three types of conventional jet fuels [2]:(i) represents a real challenge because practical jet fuels are a kerosene type, (ii) a high-flash point kerosene, and (iii) a complex mixtures of several hundreds of hydrocarbons broad cut. Most international civilian aviation companies including alkanes, cycloalkanes, aromatics and poly- use the kerosene type Jet A-1 whereas some military cyclic compounds. aviation fuels are very close to Jet A-1 (TR0 in France, In order to study the combustion behavior of AVTUR in the United Kingdom, and JP-8 in the United commercial jet fuels, mixtures with well defined and States of America), although they include different reproducible composition are required: we call them additives [1–3]. Actually, Jet A is used in the United ‘surrogates’ or ‘model-fuels’. For sake of simplicity, States and Jet A-1 is used in the rest of the world. The they should include a limited number of hydrocarbons important difference between Jet A and Jet A-1 concerns with a well-defined composition, and show a behavior the freezing point (K40 8C for Jet A and K47 8C for Jet similar to that of a commercial fuel. They are of A-1). All the jet fuels must meet general physical property extremely high interest since they can be utilized to specifications. Those for Jet A-1 (Appendix 1) were study the effect of chemical composition and fuel incorporated in a standard defined in 1994 as the Aviation properties on the combustion process. Application of Fuel Quality Requirement for Jointly Operated Systems surrogates to the modeling of the ignition, oxidation, (AFQRJOS) [2]. Although turbojet engines are far more and combustion of conventional jet fuels will be fuel-tolerant than SI engines, the increased operating discussed here, and the results of recent kinetic studies pressures and temperatures have rendered the modern on the oxidation of surrogate kerosene mixtures will be turbojet engines fuel-sensitive [2,4]. Therefore the presented. Finally, recent results concerning the specifications for jet fuels represent an optimal compro- reformulation of jets fuels in the context of reduced mise of properties for engine performances and safety oil availability will be presented. aspects during storage and distribution. 50 P. Dagaut, M. Cathonnet / Progress in Energy and Combustion Science 32 (2006) 48–92 Among the properties linked to the quality of C11H23. Further information can be found in previous combustion [2], specification requirements concern reports [12–14] whereas jet A-1 specifications are given volatility, viscosity and freezing point, density, heating in Appendix A. As most of the hydrocarbon mixtures value, smoke point and luminosity factor, aromatic used as a fuel, the composition of kerosene is subject to content, and thermal stability of the fuel (ASTM D variations of composition. The composition varies from 1655). Combustion in turbojet engines is characterized one source to another [15,16] and is subject to changes by the formation of soot particles which must be due to thermal instability. The specification test device minimized for several reasons: (i) soot can be harmful for jet fuel is the thermal oxidation test as described in for the engine because of carbon deposits and radiant ASTM D3241. The thermal stability of jet fuels is heat loss which can lead to hot spots or to high improved via the use of additives. Further information combustor wall temperature, (ii) soot emissions from can be found in [8,17,18]. jet engines affect high altitudes atmospheric chemistry, and (iii) soot favors radar detection of military aircrafts. 3. Formulation of kerosene surrogate fuels Fuels with high aromatics contents, especially poly- aromatics, produce more soot. This is why both the total Since specifications on kerosene only include aromatic content is limited to 22–25% and the general physical properties, many hydrocarbon mix- naphthalene content to 3% in volume. Practically, the tures can meet these specifications, although the aromatic content of JP-8 varies between 10 and 25% relative proportions of the various chemical families with a mean at 18% in volume [3]. However, the is constrained by the general physical properties. aromatic content of kerosene has increased since the Because the variations in composition may be large sixties [4] for economic reasons, and the quality of from purchase to purchase [15], a more definite kerosene is expected to deteriorate in the future with the chemical composition was found necessary for model- reducing availability of light crudes. ing and experimental studies. Mixtures of a limited Table 1 gives the main characteristics of JP-8 and Jet number of hydrocarbons have been proposed to A-1 reported by several authors [3,5–7], compared with represent