Distillation-resolved evolution of key combustion properties

Many studies demonstrate successful emulation of pre-vaporized real fuel combustion through use of fuel surrogates. These surrogates may be described by a multiplicity of non-unique multicomponent formulations, each with pre-vaporized combustion behaviors that are essentially equivalent to the target real fuel and each other. However, many combustion applications employ fuel sprays, leaving some question as to the validity of pre-vaporized assumptions for these conditions. In the present work, a batch distillation model for ideal liquids is developed to predict the evolution of surrogate fuel combustion properties such as autoignition propensity (represented by an effective RON or DCN), hydrogen-carbon-oxygen atomic ratios, average molecular weight (MW), etc. Simulations reveal that, among several effectively equivalent pre-vaporized surrogates, large disparities may exist in one or more combustion properties as the fuels distill. For example, three multicomponent 95 RON gasoline surrogates show distillation-resolved RONs spanning, respectively, 91.0, 93.5 and 94.0 to 120.0, each with a sustained depression from the pre-vaporized 95 RON target over ∼60-70% of the distillation curve. A jet fuel example is also considered herein. Whether or not preferential vaporization effects are attenuated by the complex combustion environments encountered in many applications remains an open question; however, present results indicate a significant potential for chemical property stratification in spray combustion environments.