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Particulate Emissions from Homogeneous Charge Compression Ignition (HCCI) combustion are routinely assumed to be negligible. It is shown here that this is not the case when HCCI combustion is implemented in a direct injection gasoline engine. The conditions needed to sustain HCCI operation were realized using the negative valve overlap method for trapping high levels of residual exhaust gases in the cylinder. Measurements of emitted particle number concentration and electrical mobility diameter were made with a Cambustion DMS500 over the HCCI operating range possible with this hardware. Emissions of oxides of nitrogen, carbon monoxide and unburned hydrocarbons were also measured. These data are presented and compared with similar measurements made under conventional spark ignition (SI) operation in the same engine. Under both SI and HCCI operation, a significant accumulation mode was detected with particle equivalent diameters between 80 and 100 nm.

This paper presents the findings of theoretical and practical studies of an exhaust-gas reforming process, as applied to hydrocarbon fuels. It is shown that hydrogen-containing gaseous reformed fuels can be produced by the interaction of hot combustion products and an n-heptane feedstock in a small-scale catalytic reforming reactor. Predicted and observed reformed fuel chemical compositions were found to correlate well at the lower reactor space velocities tested, where chemical equilibrium conditions can be closely approached. Under these conditions, respective hydrogen and carbon monoxide yields of around 32 and 20 volume per cent were obtained. Under certain conditions, it was found that carbon solids were deposited on the reforming catalyst. Measures taken to avoid this problem included changes in the reforming oxidant to fuel ratio, and the addition of excess steam to the oxidant composition.