Methodology to account for multi-stage ignition phenomena during simulations of RCM experiments

Abstract

RCM experiments are used to investigate the ignition behavior of fuels at engine relevant conditions. Modern designs utilize pistons with crevice volumes machined around the circumference of the crown in order to suppress boundary layer effects during the volumetric compression process. While piston crevices have been successful in controlling heat loss from the reaction chamber gases and improving the overall homogeneity of the reacting mixture, multi-stage ignition events can be sufficiently perturbed by spatial non-uniformities and there can be substantial gas flow into the crevice volume due to the preliminary, or low-temperature heat releases. Ignition delay times can be lengthened by up to 25% as a result of these effects. These features are difficult to incorporate into 0D chemical kinetic simulations where volumetric expansion curves from non-reacting experiments are often used to prescribe the heat loss characteristics of reacting chamber mixtures. A new methodology is presented here to account for multi-stage ignition phenomena during simulations of RCM experiments. The approach and a range of demonstrative examples are presented in this study.