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Future fuel formulations including classic refining schemes (hydrotreatment) and synthetic blending stocks like Fischer-Tropsch, oligomerate and high cetane linear ethers were tested for their impact on diesel emissions in various engine conditions (transient and cold operations). CO, HC, Aldehyde, Particulate and PAH emissions are highly sensitive to fuel quality whereas NOx emissions are only slightly modified. Very low level of pollutants is obtained with the Fischer-Tropsch fuel. Oligomerisation fuel induces an increase in CO, HC, aldehyde emissions due to its very low cetane number but presents low emissions of particulates and smoke because of its paraffinic composition. Pentyl ether behaves essentially as a high cetane paraffinic hydrocarbon. The relationships between fuel parameters and emissions were also assessed: CO, HC and aldehyde emissions depend on the cetane number. Particulates, IOF, smoke and PAHs are controlled by aromatic content and density.

The impact of fuel hydrotreatment on Diesel exhaust emissions is investigated. Several fuels are formulated in a refining pilot unit. By progressively increasing the hydrotreatment severity, sulfur reduction is first achieved, followed by aromatic reduction and cetane enhancement. The operating conditions and the effect on fuel characteristics are detailed. The influence of this hydrotreatment on exhaust emissions of a light-duty prechamber engine is studied under both steady-state and transient conditions. In steady-state operation, a slight effect of fuel on CO and HC emissions appears which increases when the injection timing is retarded. No evidence of fuel influence on particulate emissions is found except for a sharp increase due to sulfate contribution for fuels with high sulfur content. The transient operation enhances the influence of fuel characteristics on pollutants.