Gasoline is among the world’s most prolific liquid transportation fuels. However, a fundamental understanding of its burning characteristics is still lacking. A major complication is that gasoline is highly multicomponent and comprised of hundreds of chemical species. It also has a seasonable variability in its composition. Calibration fuels have been developed to address some of these concerns for establishing emissions and fuel economy standards for engines.<br/>This study presents results of experiments and detailed numerical modeling for a 93 octane gasoline calibration fuel and its surrogates using the configuration of an isolated droplet burning under conditions that promote a one-dimensional gas transport created by fuel evaporation from the droplet surface. The data are used to validate a kinetic mechanism comprised of 17K reactions for the certification fuel surrogates. The numerical modeling included multicomponent phase equilibrium, unsteady gas and liquid transport, radiative heat transfer, internal liquid diffusion and soot chemistry to predict the formation of soot aggregates and the soot shell. The simulations were compared with experimental measurements for initial droplet diameters between 0.55 mm and 0.60 mm. The droplets were spark-ignited and their burning histories were recorded by digital video imaging with quantitative data obtained by computer-based image analysis.<br/>Experimental results showed that the calibration fuel and surrogates have very close burn rates and flame diameters. Predictions of the soot shell in which aggregates reside by a balance of forces acting on them (due to Stefan drag and thermophoresis) were in reasonable agreement though slightly over-predicted. The study shows the efficacy of using droplet burning data to validate kinetic mechanisms of surrogates for gasoline certification fuels.

Experiments and numerical modeling of surrogate droplet combustion for a 93 octane gasoline calibration fuel

ACS Fall 2021

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