Global Reduced Model for Conventional and Alternative Jet and Diesel Fuel Autoignition

Abstract

A global reduced model for the autoignition of conventional petroleum-derived and alternative, hydroprocessed and Fischer–Tropsch, jet and diesel fuels is presented. The model is based on a seven-step model from the literature (Zheng, J.; Miller, D. L.; Cernansky, N. P. A Global Reaction Model for the HCCI Combustion Process, SAE Paper 2004-01-2950, 2004) and includes steps to predict oxidation and autoignition in the three temperature regimes of interest to engine applications, the high-, low-, and negative-temperature-coefficient (NTC) regimes. Here we have included dependence of reaction rate parameters on the derived cetane number (DCN) to predict the influence of fuel variability on autoignition and optimized the reduced model to best fit target shock tube ignition delay time data for jet and diesel fuels. The standard deviation between model predictions for ignition delay and the target shock tube data set is ±21% and the model captures all experimental trends for ignition delay variation with DCN, temperature, pressure, and fuel–air equivalence ratio in all temperature regimes. Comparisons to experimental ignition delay time data not contained in the target data set show model–experiment deviation similar to the comparisons with the target data, with global standard deviation of ±20–30% and differences of at most a factor of 2. The model comparisons with shock tube data suggest that the model is suitable for autoignition prediction for fuels containing large quantities of aliphatic compounds with DCN = 30–80 for 650–1300 K, 8–80 atm, and fuel–air equivalence ratios of 0.25–1.5.