Analysis of Ethanol Blending Effects on Auto-Ignition and Heat Release in n-Heptane/Ethanol Non-Premixed Flames

This study delves into the auto-ignition temperature of n-heptane and ethanol mixtures within a counterflow flame configuration under low strain rate, with a particular focus on the impact of ethanol blending on heat release rates. Employing the sensitivity analysis method inspired by Zurada's sensitivity approach for neural network, this study identifies the group of critical species influencing the heat release rate. Further analysis concentration change reveals the intricate interactions among these various radicals across different temperature zones. It is found that, in n-heptane dominant mixtures, inhibition of low-temperature chemistry (LTC) caused by additional ethanol, impacts heat release rate at high temperature zone through diffusion effect of specific radicals such as CH2O, C2H4, C3H6 and H2O2. For ethanol-dominant mixtures, an increase in heat release rate was observed with higher ethanol fraction. Further concentration change analysis elucidated it is primarily attributed to the decomposition of ethanol and its subsequent reactions. This research underscores the significance of incorporating both chemical kinetics and species diffusion effects when analyzing the counterflow configuration of complex fuel mixtures.