Comprehensive Characterization of Particulate Emissions from Advanced Diesel Combustion

The applicability of several popular diesel particulate matter (PM) measurement techniques to low temperature combustion is examined. The instruments' performance in measuring low levels of PM from advanced diesel combustion is evaluated. Preliminary emissions optimization of a high-speed light-duty diesel engine was performed for two conventional and two advanced low temperature combustion engine cases. A low PM (<0.2 g/kg_fuel) and NO_x (<0.07 g/kg_fuel) advanced low temperature combustion (LTC) condition with high levels of exhaust gas recirculation (EGR) and early injection timing was chosen as a baseline. The three other cases were selected by varying engine load, injection timing, injection pressure, and EGR mass fraction. All engine conditions were run with ultra-low sulfur diesel fuel.

An extensive characterization of PM from these engine operating conditions is presented. Real-time mass concentration, filter based mass, filter chemical speciation, and particle size distribution analyses were performed. Advanced LTC PM proved to differ significantly from conventional diesel combustion PM by having smaller average particle size and higher organic content. Particulate from conventional diesel combustion matched published trends in particle sizes and chemical content. Between conventional diesel cases, increased load caused higher mass concentration, larger mean particle diameter, and decreased organic content. Increased injection pressure between LTC cases resulted in lower PM mass concentrations, smaller particle sizes, and higher organic content.