Effect of furans on particle formation in diffusion flames: An experimental and modeling study

Furans have recently raised as possible transportation fuels which can be produced from biological sources and biotechnological methods. Their role on combustion-generated particle formation results quite unexplored. Few studies showed that dimethylfuran (DMF) among the other furanic hydrocarbons seems to have a great tendency to form soot precursors. This unexpected trend should be kept in mind before a further usage of furans, especially DMF, as transportation fuels. The effect of furans as substituent to traditional fuels has been investigated both experimentally and numerically in a counter-flow diffusion flame. Furan, 2-methylfuran and 2,5-dimethylfuran have been chosen as standards for furanic fuels. Optical techniques, previously validated, namely laser induced fluorescence and incandescence, have been adopted to detect small nanoparticles and soot aggregates, respectively. On the modeling part, a sectional approach has been used to confirm the sooting tendency experimentally found for the investigated fuels. A gas phase kinetic mechanism available in literature for oxidation and decomposition of furans has been integrated in a recently developed detailed kinetic mechanism for particulate formation. Experiments confirmed by model show that furanic fuels increase particle production. Furan has the lowest impact on the particle production whereas 2,5-dimethylfuran and 2-methylfuran show a higher propensity; in particular, 2-methylfuran has a greater tendency to produce particles with respect to 2,5-dimethylfuran. Modeling analysis showed that 2-methylfuran produces large amounts of C4-species and thus benzene and polycyclic aromatic hydrocarbons (PAHs). 2,5-dimethylfuran mainly forms phenol during its decomposition, which leads to cyclopentadiene and thus naphthalene formation. However, in the operating conditions analyzed in this study the overall PAHs and first particle production result less strong than in 2-methylfuran. However, different combustion conditions can change the effectiveness of these channels and might invert the particle production tendency of furanic fuels. (C) 2014 The Combustion Institute. Published by Elsevier Inc. All rights reserved.