Soot reduction effects of dibutyl ether (DBE) addition to a biodiesel surrogate in laminar coflow diffusion flames

The dibutyl ether (DBE) has been recently identified as an alternative biofuel produced from lignocellulosic biomass. In the present study, experimental and chemical kinetics studies were carried out to investigate the effects of dibutyl ether addition to a biodiesel surrogate (methyl decanoate) on soot formation in laminar coflow diffusion flames. The mole fraction of DBE in the fuel stream varies from 0 to 40 mol%. Laser-induced incandescence (LII) technique was applied to obtain the 2D soot volume fraction distribution and a combined methyl decanoate-dibutyl ether-PAH kinetic model was constructed to analyze chemical effects of DBE addition on the concentration of key species for soot inception and growth. The experimental results show that DBE addition can indeed reduce the soot yielding and the suppressive effect is nonlinear with the mole fraction of DBE in the fuel mixture. It is found that in the flame centerline, soot reduction with more DBE addition is a combined effect of lower nucleation rate and decreasing PAHs condensation, while soot reduction effect is somewhat moderate in flame wings as the result of the competition between decreasing inception rate and enhanced surface growth caused by higher acetylene concentration. Reaction path analysis suggests that DBE addition can markedly suppress C-3 + C-3 pathways to the first aromatic ring, lead to lower A1 yield and consequently limit the aromatic growth to larger PAHs. DBE is found to be remarkably promising in terms of suppressing soot formation and reducing particle emission. (C) 2018 The Combustion Institute. Published by Elsevier Inc. All rights reserved.