Diesel fuel quality and its relationship with emissions from diesel engines
CONCAWE predicts future (year 2000) diesel fuel properties to heessentially in the range of 43 to 54 cetane number (median value: 48.5) and 0.825 to 0.870 density (median value: 0.846). Compared with present average commercial European diesel fuels this means a drop in cetane number by 2 and an increase in density by0.006, however the spread in quality remains similar.Operating costs for the EEC oil industry to compensate for these changes would amount to some $US 38 to 45 mil.lion per year if ignition improvers were employed and $US 1.3 to 1.7 billion/year if hydrogenation processes were installed. The latter figure is based on capital costs of some $US 3.5 to 4.5 billion. The ignition improver approach is clearly less expensive than the processing route but it will not change other parameters such asdensity/aromaticity. The costs and energy requirements to compensate for the anticipated changes in diesel fuel quality are very high when compared to any marginal improvement in emissions performance of today’s engines.Updating the diesel engine homologation fuel specification to reflect changes in commercial fuel properties would reliably ensure that certified emissions standards will be met in the field,despite variations in fuel quality. In addition, advances in engine technology, which are already emerging in the USA, represent viable measures for improving the emissions performance of diesel engines.