THE ETHANOL EFFECT ON PARTICLE SIZE DISTRIBUTIONS IN ETHYLENE PREMIXED FLAME

In the present study a laminar premixed rich ethylene flame was doped with different amounts of pre-vaporized ethanol, with the aim to understand the influence of biofuels on both the total amount of particulate matter and the size distribution functions of the formed carbonaceous particles. Four different flames were investigated: one of pure ethylene as reference flame and three with an increased amount of ethanol, i.e. 10, 20 and 30% (where the percentage refer to the total carbon fed). The equivalence ratio of the four flames was kept constant at 2.01, so that the temperature profiles did not show a significant difference when the ethanol was added. The analysis of the particle size distribution functions was performed by using a nano- Differential Mobility Analyzer (nano-DMA) which allows to detect particles as small as 2 nm. The results showed general reduction of the total volume fraction of particulate when ethanol was added. Moreover, the reduction of the formed particles increased as function the amount of ethanol added. Also, looking at particle size distribution functions it was possible to observe a reduction on the particle size for the same height above the burner when ethanol was added to the flame. Comparing pure ethylene flame and ethanol doped flames at different height but with same amount of particles the particle size distribution functions appear to be quite similar. This indicates that in premixed flames ethanol mostly affect gas phase chemistry and consequently formation of incipient particles.