Autoignition measurements and a validated kinetic model for the biodiesel surrogate, methyl butanoate

Abstract

The autoignition of methyl butanoate has been studied at 1 and 4 atm in a shock tube over the temperature range 1250–1760 K at equivalence ratios of 1.5, 1.0, 0.5, and 0.25 at fuel concentrations of 1.0 and 1.5%. These measurements are complemented by autoignition data from a rapid compression machine over the temperature range 640–949 K at compressed gas pressures of 10, 20, and 40 atm and at varying equivalence ratios of 1.0, 0.5, and 0.33 using fuel concentrations of 1.59 and 3.13%. The autoignition of methyl butanoate is observed to follow Arrhenius-like temperature dependence over all conditions studied. These data, together with speciation data reported in the literature in a flow reactor, a jet-stirred reactor, and an opposed-flow diffusion flame, were used to produce a detailed chemical kinetic model. It was found that the model correctly simulated the effect of change in equivalence ratio, fuel fraction, and pressure for shock tube ignition delays. The agreement with rapid compression machine ignition delays is less accurate, although the qualitative agreement is reasonable. The model reproduces most speciation data with good accuracy. In addition, the important reaction pathways over each regime have been elucidated by both sensitivity and flux analyses.