Sooting Behavior of Oxygenated Fuels in a Diffusion Burner

Different strategies are being investigated towards reducing engine-out emission levels of soot and NOx of modern Diesel engines. A fuel-based strategy currently under investigation, entails the use of low cetane number (CN; i.e. low reactive) oxygenates. Previous research has shown that low CN oxygenates (e.g. cyclohexanone, X1), compared to their higher CN counterparts, perform exceptionally well with respect to abating soot emissions. An accepted mechanism, which could account for the observed reduction, is associated with the ignition delay (ID). As the ID effect does not apply to burners, experiments with various oxygenated blends over a wide range of CN’s in a yellow (diffusion) flame burner have been conducted to establish whether or not this is the only mechanism responsible for the measured soot reduction. From the experiments can be observed that emitted soot mass is closely correlated to CN in burners as well. Accordingly, the results suggest that another mechanism is, at least partially, responsible for the observed reduction in emitted soot mass.