Ignition delay times of low alkylfurans at high pressures using a rapid compression machine

Auto-ignition behavior of 2-ethylfuran (EF) was investigated in the low to intermediate temperature range (766-1013 K) over equivalence ratios of 0.5, 1.0, and 2.0 at 16 and 30 bar using a rapid compression machine. Equivalence ratio was varied by changing the mole fractions of O₂ while fixing the fuel fraction. The fuel did not show "negative temperature coefficient (NTC)" or two stage ignition behavior in the present measuring range. Simulations were conducted on the basis of the alkylfuran mechanism of Somers et al. (2013) [1], in which the EF sub-mechanism is not fully developed. Optimization of the EF sub-mechanism was attempted. Results show that the modified mechanism shows better agreement with our measurements and other data in the literature. Comparison of the reactivity of EF with that of 2-methyl furan (MF) and 2, 5-dimethyl furan (DMF) under various equivalence ratios was conducted and results show that the relative reactivity of the three furanic fuels depends complicatedly on both equivalence ratio and temperature, which was further interpreted by examining the ignition kinetics. As DMF is more branched, H-abstractions contribute most to the fuel consumption. For EF and MF, OH-additions at C2 and C5 positions dominate the reaction pathways. From reaction flux analyses, the reactions involving alkyl side chains of alkylfurans are analogous with those of alkylbenzenes at low to intermediate temperature oxidation conditions. Moreover, large amount of alkylfurans go through OH-addition reactions on the ring, which is not observed in the reaction pathways of alkylbenzenes.