Abstract.

In a CONCAWE programme the influence of typical European diesel fuels on emissions performance was investigated with six modern diesel passenger cars, equipped with oxidation catalysts.

The investigation was conducted using the European ECE 15 + EUDC test procedure and steady-state driving with seven fuels having key properties in the range of 48 to 54 for cetane number, 0.834 to 0.850 kg/l for density and 337 to 367°C for the 95% Pt. Six fuels were adjusted to a sulphur level of 0.05% m (mandated from 1996 on), one fuel was doped to a 0.20% m sulphur content.

The study confirms that oxidation catalyst technology provides very effective control of particulate, carbon monoxide and hydrocarbon emissions. Catalysts were also found to reduce the influence of changes in fuel properties on emissions.

The influence of fuel properties on emissions was very vehicle dependent; some engines showed no significant influence of fuel changes. The fuel property which correlated best with particulates was density. Cetane number correlated with hydrocarbons and to some extent with carbon monoxide. No relationship was found between particulates and total aromatics.

PROGRAMME The harmonized European specification for diesel fuel (EN 590) has been established to improve diesel engine operation and to assist in the control of exhaust emissions. With the introduction of oxidation catalysts for diesel passenger vehicles, exhaust emissions including particulates can be effectively reduced. CONCAWE decided to study the emissions performance of a range of diesel fuels with this catalyst technology.

The investigation was conducted using the European ECE 15 + EUDC test procedure and steadystate driving with seven fuels having key properties in the range of 48 to 54 for cetane number, 0.834 to 0.850 kg/l for density and 331 to 367°C for the 95% Pt. Total aromatics content ranged from 16 to 26% volume. Six of the seven fuels were adjusted to a constant sulphur level of 0.05% mass, one fuel was doped to a 0.20% mass sulphur level. Two fuels were treated with 2-ethylhexyl nitrate ignition improver additive to provide higher cetane levels.

This range of fuels was considered to be suficiently wide and reflects the spread of typical European commercial diesel fuels to enable emissions performance with oxidation catalyst equipped passenger vehicles to be determined.

Six modern diesel passenger vehicles equipped with oxidation catalysts were used in the programme covering a range of European engine designs. The models included naturally aspirated (NA), turbocharged (TC), turbocharged and intercooled (TCJIC), indirect injection (IDI) and direct injection (DI) types.

RESULTS ON FUEL/CATALYST PERFORMANCE The emissions tests were conducted on

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