Importance of Surrogate JP-8/Jet-A Fuel Composition in Detailed Chemical Kinetics Development

Abstract

The importance of three JP-8/Jet-A surrogate fuels composition is discussed in the context of detailed chemical kinetic modeling of JP-8/Jet-A fuel autoignition and flame characteristics in a flowing system. The main objective is to assess the relative role of each compound class in the surrogates upon the prediction of auto-ignition and combustion characteristics of JP8/Jet-A fuel. The current study is also motivated by a desire to explore surrogate fuel blends for JP-8/Jet-A with the least number of chemical constituents as was reflected in the “Combustion Simulation Databases for Real Transportation Fuels” workshop (NIST, National Institute of Standards and Technology, Gaithersburg, Maryland, September 4-5, 2003). The three different JP-8/Jet-A surrogate fuel blends considered in the present study were developed by (Schulz 1991 and Violi et al. 2002). These three JP-8/Jet-A surrogate fuel blends have different normal, iso-, and cyclo-paraffins and aromatic components as given in Table I. The detailed JP-8 chemical kinetic reaction mechanism, we have been developing (Mawid et al. 2002 and 2003) for a 12-component surrogate fuel blend, has been used as a basis for the development of detailed reaction mechanisms for the other two surrogate fuel mixtures. Submechanisms for the monosubstituted aromatics such as toluene, m-xylene, butylbenzene, and for the bicyclic aromatics such as 1-methylnaphthalene were assembled and integrated with the detailed JP-8 reaction mechanism (Mawid et. al. 2002 and 2003). The new JP-8 detailed mechanisms for the three different JP-8 surrogate fuel blends were evaluated, using a lean premixed JP-8-air mixture, over a temperature range of 900-1020 K and for atmospheric pressure conditions, by predicting auto-ignition delay times in a plug flow reactor and comparing them to the available experimental data for Jet-A fuel. The results indicated that overall the six-component JP-8 surrogate 3 (Table I) can predict similar ignition-delay periods as those predicted by the 12-component JP-8 surrogate 1. The study suggests that, for the conditions considered here, the surrogate fuel blend composed of six pure hydrocarbons is as adequate to simulate the ignition characteristics of JP-8/Jet-A fuel as that of twelve pure hydrocarbons surrogate blend. The study also lends support to the suggestion that minimizing the number of chemical compounds in the surrogate fuel is very important for circumventing the lack of thermochemical and chemical kinetic parameters for JP-8/Jet-A fuels.