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To What Degree Do Changes in Gasoline Properties Affect Emissions From European Cars?
Technical Paper
943499
Sector:
Language:
French
Abstract
In response to world-wide interest in the effect of gasoline
quality on vehicle emissions, the Shell Companies carried out an
international research program to study the effect of compositional
variables of gasolines on emissions from European vehicles, whether
or not they were equipped with a catalytic converter. The
information revealed in this program was proposed as data for the
tripartite study of the European Commission that gave rise to the
EPEFE program. The chief information revealed by this study is as
follows:
Change in the quality of the gasoline can reduce average
emissions for a fleet of vehicles, but changing a single
characteristic cannot in any way reduce all emissions for all
vehicles. There is great variation in vehicle response to changes
in fuel properties, primarily with regard to NOx emissions, and
the reason for this phenomenon is still not completely understood.
A significant portion of the effects observed, especially for
NOx, appears to be the result of slight variations in AFR
appearing under transitory operation, and due to variations in the
stoichiometry of the gasolines.
CO emissions of existing vehicles can be reduced by using
peroxides, but these effects are reduced for vehicles employing the
latest technology. HC emissions appear to be lower for fuels with a
low aromatic content, but this is completely or partially
associated with changes in the distillation curve, modifications
which result from the compositional change. Reducing the aromatics
leads to a reduction in NOx emissions before the catalytic
converter, but generally leads to an increase in NOx emissions
after the catalytic converter. This is due to the lower efficiency
of catalytic converters with gasolines with a low aromatic
content.
A scientific understanding of the mechanism involved in these
phenomena is of primary importance for future optimization of the
engine/gasoline combination.