  A systematic investigation on the effects of roaming radical reactions on
global combustion properties for transportation fuels is presented. New
software was developed that can automatically discover all the possible roaming
pathways within a given chemical kinetic mechanism. This novel approach was
applied to two mechanisms taken from the literature, one for heptane and one
for butanol. Ignition delay times and laminar flame speeds were computed over a
broad range of conditions, while testing varying degrees of roaming. As the
degree of roaming is increased, the ignition delays increased, consistent with
the hypothesis that roaming decreases the reactivity of the system. The percent
increase in the ignition delay is strongly temperature dependent, with the
largest effect seen in the negative temperature coefficient regime. Outside of
this temperature range, the effect of roaming on global combustion properties
is small, on the order of a few percent for ignition delays and less than a
percent for flame speeds. The software that was used to create the new
mechanisms and test the effects of roaming on combustion properties are freely
available, with detailed tutorials that will enable it to be applied to fuels
other than heptane and butanol.
