  The relative importance index (RII) method for determining appropriate target
species for dynamic adaptive chemistry (DAC) simulations using the DRGEP method
is developed. The accuracy and effectiveness of this RII method is validated
for two fuels: n-heptane and isopentanol. The RII method determines appropriate
DRGEP target species solely from the local thermo-chemical state of the
simulation, ensuring that accuracy will be maintained. Further, the RII method
reduces the expertise required of users to select DRGEP target species sets
appropriate to the combustion phenomena under consideration. Constant volume
autoignition simulations run over a wide range of initial condi- tions using
detailed reaction mechanisms for n-heptane and isopentanol show that the RII
method is able to maintain accuracy even when traditional static target species
sets fail, and are even more accurate than expert-selected target species sets.
Additionally, the accuracy and efficiency of the RII method are compared to
those of static target species sets in single-cell engine simulations under
homogeneous charge compression ignition conditions. For simulations using more
stringent DRGEP thresholds, the RII method performs similarly to that of the
static target species sets. With a larger DRGEP threshold, the RII method is
significantly more accurate than the static target species sets without
imposing significant computational overhead. Furthermore, the applicability of
the RII method to a DRG-based DAC scheme is discussed.
