Heterogeneous Surface Effects on Methanol Autoignition

An experimental study was conducted to investigate methanol autoignition including surface effects. Autoignition temperatures were determined for methanol using spherical, glass, constant volume bombs of various size, in order to assess the effects of changing the vessel surface-to-volume ratio on the minimum autoignition temperature and on the autoignition limits and ignition delays. Autoignition limit diagrams were constructed by determining the autoignition temperature for various methanol/oxygen/nitrogen mixtures. The diagrams were characterized by a minimum autoignition temperature occurring at a particular equivalence ratio, which was typically not stoichiometric. An empirical Arrhenius type expression for ignition delay was also developed and analyzed with respect to surface effects. This model was then compared with models used at higher temperatures.