Comparative Analysis of Jet Fuel Surrogates Based on a Comprehensive Kinetic Scheme

The ignition delay time (IDT) is a fundamental combustion property of a premixed system under realistic engine operating conditions. In this paper, a numerical investigation into the autoignition of a total of nine jet fuel surrogates is conducted, and a definition of "error function (E)" is introduced to quantitatively analyze the agreement between calculated values by surrogates and measured data of Jet A/JP-8. Besides, a sensitivity analysis is carried out for IDT to reveal the dominant reactions of autoignition behavior, and the sensitivity coefficient of a specific reaction is obtained, as well as the similarity index for 36 surrogate pairings. With a kinetic scheme from the CRECK modeling group, each surrogate is observed to present a comparable E value, indicating their similar capability to describe the autoignition characteristics of jet fuel across a wide range of conditions. What is more, from a similarity index perspective, it is also noticed that there is a great deal of similarity between any two surrogates. A series of comparisons on IDT sensitivity spectra between a pair of surrogates which have similar chemical compositions are conducted at last. On the basis of these results, a speculation is proposed that polyalkylated benzene is more suitable than monoalkylated benzene as the representative of aromatics in the jet fuel surrogate, and iso-alkane other than cycloalkane ought to be a major consideration in addressing the development of a surrogate fuel. Therefore, what we recommend is that a rational jet fuel surrogate should be composed of n-alkane, iso-alkane, and aromatics, and the selected representative components for aromatics will be given to polyalkylated benzene, such as m-xylene and 1,2,4-trimethylbenzene.