Influence of the Molecular Structure of Hydrocarbon Fuels on Diesel Exhaust Emissions

Abstract

The influence of the molecular structure of hydrocarbon fuels on soot, SOF, and NOx emissions from a diesel engine was analyzed while ignition lag and other physical fuel properties were kept constant. Mixtures of normal paraffin (n-tetradecane) and isoparaffin (heptamethylnonane) were used as a base fuel and one of 5 kinds of hydrocarbons including mono-aromatic, diaromatic, and non-aromatic was added. The aromatic compound content varied in the range of 0~60 vol% for the mono-aromatic fuel and 0~40 vol% for the diaromatic fuels. The experimental results showed that regardless of the molecular structure of the fuel, both particulate and NOx emissions increased linearly with the C/H atomic ratio of fuels under constant ignition lag. The increase in particulate emissions with C/H atomic ratio was caused by increase in the amount of dry soot. SOF, THC, and BSEC were not very much affected by the C/H atomic ratio and molecular structure of the fuels. The fuel properties discussed here showed similar results both in DI and IDI engines. © 1994, The Japan Society of Mechanical Engineers. All rights reserved.