Effect of Ethanol Addition on the Laminar Burning Velocity of Gasoline Surrogates With Toluene

Abstract

Laminar burning velocity (LBV) is a crucial parameter in many practical combustion simulations, and the acquisition of LBVs is a critical step for evaluating potential alternative fuels and/or suitable surrogates. Ethanol is regarded as one of the most promising alternative fuels, particularly for spark ignition engines, as it may be produced from renewable biomass. While there exists data showing the pressure dependence on ethanol’s LBV compared to iso-octane and n-heptane (primary reference fuels (PRFs)), the relative magnitude of the pressure dependence of LBV between ethanol and toluene has not been established. The inclusion of toluene is important because commercial gasoline has significant levels of aromatics. In this work, common gasoline surrogate components of iso-octane, n-heptane, toluene, and ethanol were studied as pure compounds and in equal volume binary, ternary, and quaternary mixtures. Experiments are conducted in a spherical combustion bomb at elevated temperatures (380 K and 450 K) and pressures (1 to 4 bar). Under these conditions, ethanol and n-heptane present faster LBVs than iso-octane and toluene, particularly at 450 K. Ethanol and iso-octane present strong pressure dependence, with this effect accentuated at higher temperature conditions. As equal volume mixtures were studied, the effect of these distinct behaviours was examined in comparison to chemical kinetic predictions and widely used mixing rules.

Effects of oxygenate and aromatic content on engine-out aldehyde emissions from pure, binary, and ternary mixtures of ethanol, toluene, and iso-octane

“…Specif-ically, during the low temperature heat release, the reactivity of ethanol is suppressed but the reactivity of toluene is significantly enhanced [39]. Similar observations have been made when studying the laminar burning velocity of equal-volume binary and ternary mixtures of iso-octane, ethanol, and toluene at 380 K and 450 K [40,41,42]. As Sarathy et al found, in this region, ethanol favours chain termination pathways leading to acetaldehyde [7].…”