An investigation of phase-change behavior in RCM experiments with large molecular weight fuels

摘要

Rapid compression machines (RCMs) are well-suited for acquiring validation targets for chemical kinetic models at the operating conditions of current and future internal combustion engines. However, probing the gas-phase chemistry of transportation relevant fuels in these devices has been challenging due to the involatility of constituent or surrogate species. This challenge has been addressed via heating of the apparatus and accompanying pre-mixing tank, while experiments utilizing fuel aerosols have also been suggested as a viable approach. The effect of phase change during experiments with these large molecular weight fuels using either fuel loading method, on the well-defined "adiabatic core" of the reaction chamber has not been previously assessed. This study attempts to do so where a computational approach is utilized and several representative conditions are investigated. A new model is developed to facilitate this study, where the multi-phase species and energy transport are modeled. Simulated stratification profiles are presented for mixtures containing two diesel surrogates, n-dodecane and n-hexadecane. For the conditions explored here, it is found that a thermally and compositionally well-defined "adiabatic core" can be maintained throughout the duration of a typical experiment.