The Effect of Fuel Type and Aftertreatment Method on Ultrafine Particle Emissions from a Heavy-Duty Diesel Engine

Two potential strategies for reducing diesel emissions are exhaust aftertreatment and the use of reformulated or alternative fuels. Little is yet known about the impact on ultrafine particle emissions of combining exhaust aftertreatment with such increasingly common fuels. This paper reports ultrafine particle size distribution measurements for a study in which the impact of such fuels on emissions from a heavy duty diesel engine employing different aftertreatment configurations was evaluated. Eight different fuels were tested: Canadian No. 1 and No. 2 diesel; low sulfur diesel fuel; two different ultra low sulfur diesel fuels (< 30 ppm S); Fischer-Tropsch diesel fuel; 20% biodiesel blended with ultra low sulfur diesel fuel; and PuriNO(x)(TM). The fuels were tested in combination with four exhaust configurations: engine out, diesel oxidation catalyst ( DOC), continuously regenerating diesel particle filter ( CRDPF), and engine gas recirculation with CRDPF ( EGR-DPF). In general, aftertreatment configuration was found to have a greater impact on ultrafine particle size distributions than fuel composition, and the effects of aftertreatment tended to be uniform across the entire particle size distribution. Steady state tests revealed complex behavior based on fuel type, particularly for PuriNOx. This behavior included bimodal particle size distributions with modes as low as 8-10 nm for some fuels. Unlike previous results for gravimetric PM from this study, no significant correlation for ultrafine emissions was found for fuel properties such as sulfur level.