  The autoignition delays of iso-butanol, oxygen, and nitrogen mixtures have
been measured in a heated rapid compression machine (RCM). At compressed
pressures of 15 and 30 bar, over the temperature range 800-950 K, and for
equivalence ratio of $\phi$ = 0.5 in air, no evidence of an NTC region of
overall ignition delay is found. By comparing the data from this study taken at
$\phi$ = 0.5 to previous data collected at $\phi$ = 1.0 (Weber et al. 2013), it
was found that the $\phi$ = 0.5 mixture was less reactive (as measured by the
inverse of the ignition delay) than the $\phi$ = 1.0 mixture for the same
compressed pressure. Furthermore, a recent chemical kinetic model of
iso-butanol combustion was updated using the automated software Reaction
Mechanism Generator (RMG) to include low- temperature chain branching pathways.
Comparison of the ignition delays with the updated model showed reasonable
agreement for most of the experimental conditions. Nevertheless, further work
is needed to fully understand the low temperature pathways that control
iso-butanol autoignition in the RCM.
