Effects of a ceramic particulate trap and copper fuel additive on heavy-duty diesel emissions

摘要

This research quantifies the effects of a copper fuel additive on the regulated [Oxides of nitrogen (NO_x), hydrocarbons (HC) and total particulate matter (TPM)] and unregulated emissions [soluble organic fraction (SOF), vapor phase organics (XOC), polynuclear aromatic hydrocarbons (PAH), nitro-PAH, particle size distributions and mutagenic activity] from a 1988 Cummins LTA10 diesel engine using a low sulfur fuel. The engine was operated at two steady state modes (EPA modes 9 and 11, which are 75 and 25% load at rated speed, respectively) and five additive levels (0, 15, 30, 60 and 100 ppm Cu by mass) with and without a ceramic trap. Measurements of PAH and mutagenic activity were limited to the 0, 30 and 60 ppm Cu levels. Data were also collected to assess the effect of the additive on regeneration temperature and duration. Copper species collected within the trap were identified and exhaust copper concentrations quantified. The fuel additive had little effect on baseline emissions (without the trap) of TPM, SOF, XOC, HC or NO_x. Particle size distributions indicated that there was a trend towards more nuclei mode particles with increasing additive level, but an overall increase in mass emissions was not detected. Use of the additive generally resulted in reductions of PAH in both the SOF and XOC. Additive effects on mutagenic activity appeared to be mode dependent, with decreases in activity at mode 9 and relatively little change at mode 11. The trap reduced TPM from 72 to 93% compared to baseline, had no effect on NO_x, and reduced HC about 30% at mode 9 with no consistent change at mode 11. The trap's SOF removal efficiency was greater at mode 9 (84 to 91%) than at mode 11 (55 to 88%). The XOC reductions were less than 48% at mode 9, with mode 11 again showing no consistent change. Collection of copper by the trap was greater than 95%, resulting in a 44 μg/m~3 emission rate at mode 9 with 100 ppm copper in the fuel. Pah were generally reduced in the SOF by the trap, but displayed no change or were slightly increased in the XOC. As found in previous studies at MTU with traps, the particle and vapor phase associated mutagenic response generally decreased over time with continued use of the trap (this occurred at all additive levels in this study). The additive reduced the trap regeneration temperature from 510°C to about 375°C and reduced the regeneration time from about 90 minutes with no additive to about 1 minute with 30 ppm and greater additive concentrations. Trap ash analysis showed that approximately 89.5% of the material was CuO, 2.5% was Cu_2O, and 8% was CaSO_4.