  Autoignition experiments for n-butanol have been performed using a heated
rapid compression machine at compressed pressures of 15 and 30 bar, in the
compressed temperature range of 675-925 K, and for equivalence ratios of 0.5,
1.0, and 2.0. Over the conditions studied, the ignition delay decreases
monotonically as temperature increases, and the autoignition response exhibits
single-stage characteristics. A non-linear fit to the experimental data is
performed and the reactivity, in terms of the inverse of ignition delay, shows
nearly second order dependence on the initial oxygen mole fraction and slightly
greater than first order dependence on initial fuel mole fraction and
compressed pressure. Experimentally measured ignition delays are also compared
to simulations using several reaction mechanisms available in the literature.
Agreement between simulated and experimental ignition delay is found to be
unsatisfactory. Sensitivity analysis is performed on one recent mechanism and
indicates that uncertainties in the rate coefficients of parent fuel
decomposition reactions play a major role in causing the poor agreement. Path
analysis of the fuel decomposition reactions supports this conclusion and also
highlights the particular importance of certain pathways. Further experimental
investigations of the fuel decomposition, including speciation measurements,
are required.
