Effect of 2,5-dimethylfuran doping on particle size distributions measured in premixed ethylene/air flames

Biofuels, as alternative source of energy to fossil fuels, when burned in retrofitted combustion devices, have to respect the emission standards in terms of gaseous and particulate by-product emissions. Experimental findings show that biofuels generally decrease the amount of particulate matter produced and emitted from combustion systems. However small particle formation seems not inhibited in biofuel combustion and, in particular conditions, the use of biofuels even increases combustion-formed nanoparticle production. New biofuel formulations have recently identified 2,5-dimethylfuran (DMF) as possible substitute of ethanol in the spark ignition engine due to low cost production and high energy density. In lab scale reactors and flames, DMF showed different sooting tendencies depending on the combustion conditions. In this work a new sampling system has been setup to measure particle size distribution (PSD) in premixed flames at atmospheric pressure doped with DMF, from non-sooting to fully sooting conditions to better understand the particle evolution in a wide range of combustion conditions. PSDs of neat ethylene/air flames measured with the current setup are in agreement with those present in literature. Overall, experimental results show that the use of DMF reduces significantly the amount of large parti-cles produced, reducing the total mass of particles emitted. However, DMF is not reducing significantly the number concentration of particles smaller than 10 nm. Their contribution to the total mass is insignificant whereas they dominate the number PSDs. The current findings are in agreement with recent optical measurements performed in the same conditions. Although a systematic kinetic study of gas phase by-product was not possible due to lack of experimental data for the gas phase, this effect has been attributed to some oxidation pathways particularly favored in the investigated conditions that subtracts carbon from the molecular growth, thus explaining the reduced amount for particles formed in the DMF flames. (C) 2016 by The Combustion Institute. Published by Elsevier Inc.