Rapid Compression Machines (RCMs) are extensively used to study autoignition chemistry at low-to-intermediate temperatures. Over the last two decades, experimental data of the nature of species evolution profiles and ignition delays from RCMs has been used to develop and validate chemical kinetic mechanisms at low-to-intermediate temperatures and elevated pressures. A significant portion of this overall dataset is from RCMs that had not employed creviced piston to contain the roll-up vortex. The detrimental influence of the roll-up vortex and thermokinetic interactions due to the resulting temperature non-homogeneity during the negative temperature coefficient (ntc) regime have been documented in the literature. However, the adequacy of the homogeneous modeling of RCMs without creviced pistons during reactive conditions has not been investigated. In this work, computational fluid dynamics simulations of RCM without a creviced piston are conducted for nonreactive as well as nonreactive conditions. A skeletal mechanism of n-heptane is used and simulations are conducted over a range of compressed gas temperatures spanning the entire ntc regime. The results from the CFD simulations are compared with homogeneous modeling that include compression stroke and post-compression heat loss. The comparisons reveal significant quantitative discrepancy particularly for the second-stage ignition delay. This work highlights that the experimental data from RCMs without creviced piston may not be reliably interpreted for quantitative validation and refinement of kinetic mechanism.
展开▼
