Title: Reduced chemistry for butanol isomers at engine-relevant conditions,
Abstract: Butanol has received significant research attention as a second-generation
biofuel in the past few years. In the present study, skeletal mechanisms for
four butanol isomers were generated from two widely accepted, well-validated
detailed chemical kinetic models for the butanol isomers. The detailed models
were reduced using a two-stage approach consisting of the directed relation
graph with error propagation and sensitivity analysis. During the reduction
process, issues were encountered with pressure-dependent reactions formulated
using the logarithmic pressure interpolation approach; these issues are
discussed and recommendations made to avoid ambiguity in its future
implementation in mechanism development. The performance of the skeletal
mechanisms generated here was compared with that of detailed mechanisms in
simulations of autoignition delay times, laminar flame speeds, and perfectly
stirred reactor temperature response curves and extinction residence times,
over a wide range of pressures, temperatures, and equivalence ratios. The
detailed and skeletal mechanisms agreed well, demonstrating the adequacy of the
resulting reduced chemistry for all the butanol isomers in predicting global
combustion phenomena. In addition, the skeletal mechanisms closely predicted
the time-histories of fuel mass fractions in homogeneous compression-ignition
engine simulations. The performance of each butanol isomer was additionally
compared with that of a gasoline surrogate with an antiknock index of 87 in a
homogeneous compression-ignition engine simulation. The gasoline surrogate was
consumed faster than any of the butanol isomers, with tert-butanol exhibiting
the slowest fuel consumption rate. While n-butanol and isobutanol displayed the
most similar consumption profiles relative to the gasoline surrogate, the two
literature chemical kinetic models predicted different orderings.