Main content area

Semidetailed Kinetic Model for Gasoline Surrogate Fuel Interactions with the Ignition Enhancer 2-Ethylhexyl Nitrate

Andrae, J. C. G.
Energy & Fuels 2015 v.29 no.6 pp. 3944-3952
chemical structure, combustion, gasoline, kinetics, models, nitrates, temperature, toluene
A semidetailed chemical kinetic model has been developed describing the interaction of gasoline surrogate fuels with the ignition enhancer 2-ethylhexyl nitrate (2EHN). The model, which consists of 788 reactions among 157 species, has been checked for validity using ignition delay data obtained in a shock tube for the fuel n-heptane and rapid compression machine for primary and toluene reference fuels. The validation showed that the model can predict the reactivity trends in the measured data including differences observed between different fuels and operating conditions, which is an improvement compared to previous models for this system in the literature. The kinetic model has been used to study the effect of fuel sensitivity on the ignition delay when 2EHN is added to a gasoline surrogate fuel with a constant research octane number of 95. The efficiency of 2EHN is a nonlinear function of temperature that increases with fuel sensitivity and doping level. This is interpreted by results from a kinetic analysis which shows that, as fuel sensitivity increases, key chain branching reactions become more important. At lower temperatures (<740 K), the efficiency of 2EHN decreases with pressure and fuel sensitivities >2. Results from a brute force sensitivity analysis on the kinetics indicate that this can be related to a lower value of the inverse pressure exponent for the ignition delay time with increasing fuel sensitivity. Moreover, the kinetic analysis shows that reactions involving the 3-heptyl radical become inhibitory or less promoting while increasing the fuel sensitivity. The results presented in this work provide important information for development of advanced combustion engines such as homogeneous charge compression ignition (HCCI).