THE EFFECT OF AROMATIC-HYDROCARBONS ON SOOT FORMATION IN LAMINAR DIFFUSION FLAMES AND IN A DIESEL-ENGINE

Results are presented from tests aimed at evaluating the chemical effe cts of aromatic components on soot formation in laminar diffusion flam es and in an experimental diesel engine, The objectives of the three s ets of tests were: to evaluate the sooting tendency of (1) binary mixt ures of alkane and aromatic compounds, or alcohols and aromatic compou nds, consumed in laminar diffusion flames; (2) various diesel-fuel ble nds consumed in laminar diffusion flames; and (3) binary mixtures of a lkane and aromatic compounds consumed in a diesel engine. The results from the first set of tests showed that the sooting tendency of the bi nary mixtures is very sensitive to the proportion of aromatic compound . However, when the proportion of aromatic compound rose beyond about 10% (by volume), the flame released soot profusely, and further increa ses in aromatic proportion had no significant effect. The second set o f tests showed that various diesel fuels with aromatic content between 17 and 29% resulted in a very high laminar flame sooting tendency for all the diesel fuels tested. These results are in qualitative agreeme nt with those from the first set of tests. The third set of tests, con ducted in an experimental engine, showed that the amount of exhaust pa rticulates was insensitive to the proportion of aromatic compound, aft er variations in ignition delay had been accounted for; this is in con trast to the results from the first set, and it suggests that the grea tly enhanced air-fuel mixing present in diesel engines tends to offset the effects of fuel structure on formation of particulates.