Particle Emissions Reduction by In-Cylinder Blending of Gasoline and Diesel Fuel

Teresa  Barone, Oak Ridge National Laboratory

Particle Emissions Reduction by In-Cylinder Blending of Gasoline and Diesel Fuel

Teresa L. Barone, John M. E. Storey, Vitaly Prikhodko, Scott J. Curran, James E. Parks, and Robert M. Wagner

The use of gasoline and diesel blends in a compression-ignition engine at high load dampens fuel reactivity and allows control of combustion phasing such that engine-out particle mass and number concentration emissions are reduced. The first studies of dual-fuel combustion were carried out on single-cylinder research engines (Inagaki et al., 2006; Kokjohn et al., 2009). In the current study, we extend the analysis to a 4-cylinder, GM production engine and investigate the aftertreatment effects of a diesel oxidation catalyst (DOC). For the study, the 1.9 L engine was operated at 2300 rpm and 5.5 bar and particle emissions were sampled using a heated line and micro-tunnel dilution system. Particle number-size distributions were measured by a scanning mobility particle sizer and particle mass concentration by gravimetric analysis of Teflon?-coated quartz-fiber filters. We compared the particle emissions of dual-fuel premixed charge compression ignition (dual-fuel), premixed charge compression ignition using diesel fuel only (PCCI) and conventional diesel combustion.

The results of the study indicate the particle mass emissions for dual-fuel combustion (0.027 ? 0.007 g/hp-hr) are much less than that for conventional diesel (0.115 ? 0.016 g/hp-hr) but are similar to PCCI (0.028 ? 0.001 g/hp-hr). However, the DOC has a greater effect in reducing dual-fuel particle mass emissions (47 ? 9%) than PCCI emissions (9 ? 18%). In addition, the dual-fuel exhaust temperature was 161 ? 7 ?C cooler at the inlet of the DOC. The larger reduction by the DOC for lower exhaust temperature suggests that dual-fuel emissions consist of more organic carbon. Some of the organic carbon may have been present as nuclei-mode droplets, since the particle number-size distribution measurements show the DOC is effective in reducing the nuclei mode number concentration (35 ? 6%) but does not have an effect on accumulation mode particles. Reduction of dual-fuel nuclei mode particles is more important since their number concentration is similar to conventional diesel and PCCI values, while dual-fuel accumulation mode particles are approximately 100 times less. Thus, incorporating dual-fuel rather than conventional diesel or PCCI combustion in conjunction with DOC aftertreatment leads to fewer particle mass and number concentration emissions at high load.

Kokjohn, S., Hanson, R., Splitter, D., and Reitz, R., ?Experiments and Modeling of Dual-Fuel HCCI and PCCI Combustion Using In-Cylinder Fuel Blending?, SAE Technical Paper Series 2009-01-2647, 2009.

Inagaki, K., Fuyuto, T., Nishikawa, K., and Nakakita, K., ?Dual-Fuel PCI Combustion Controlled by In-Cylinder Stratification of Ignitability?, SAE Technical Paper Series 2006-01-0028, 2006.

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