  A novel implementation for the skeletal reduction of large detailed reaction
mechanisms using the directed relation graph with error propagation and
sensitivity analysis (DRGEPSA) is developed and presented with examples for
three hydrocarbon components, n-heptane, iso-octane, and n-decane, relevant to
surrogate fuel development. DRGEPSA integrates two previously developed
methods, directed relation graph-aided sensitivity analysis (DRGASA) and
directed relation graph with error propagation (DRGEP), by first applying DRGEP
to efficiently remove many unimportant species prior to sensitivity analysis to
further remove unimportant species, producing an optimally small skeletal
mechanism for a given error limit. It is illustrated that the combination of
the DRGEP and DRGASA methods allows the DRGEPSA approach to overcome the
weaknesses of each, specifically that DRGEP cannot identify all unimportant
species and that DRGASA shields unimportant species from removal. Skeletal
mechanisms for n-heptane and iso-octane generated using the DRGEP, DRGASA, and
DRGEPSA methods are presented and compared to illustrate the improvement of
DRGEPSA. From a detailed reaction mechanism for n-alkanes covering n-octane to
n-hexadecane with 2115 species and 8157 reactions, two skeletal mechanisms for
n-decane generated using DRGEPSA, one covering a comprehensive range of
temperature, pressure, and equivalence ratio conditions for autoignition and
the other limited to high temperatures, are presented and validated. The
comprehensive skeletal mechanism consists of 202 species and 846 reactions and
the high-temperature skeletal mechanism consists of 51 species and 256
reactions. Both mechanisms are further demonstrated to well reproduce the
results of the detailed mechanism in perfectly-stirred reactor and laminar
flame simulations over a wide range of conditions.
