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The influence of various diesel fuel properties on the steady state emissions and performance of a Cummins light-duty (ISB) engine modified for single cylinder operation has been studied at the mid-load “cruise” operating condition. Designed experiments involving independent manipulation of both fuel properties and engine control parameters have been used to build statistical engine response models. The models were then applied to optimize for the minimum fuel consumption subject to specific constraints on emissions and mechanical limits and also to estimate the optimum engine control parameter settings and fuel properties. The study reveals that under the high EGR, diffusion-burn dominated conditions encountered during the experiments, NOx is impacted by cetane number and the distillation characteristics. Lower T50 (mid-distillation temperature) resulted in simultaneous reductions in both NOx and smoke, and higher cetane number provided an additional small NOx benefit.

Previously we reported (SAE Paper 2005-01-0475) that emissions of toxicologically relevant compounds from an engine operating at low NOx conditions using Fischer-Tropsch fuel (FT100) were lower than those emissions from the engine using an ultra-low sulfur (15 PPM sulfur) diesel fuel (BP15). Those tests were performed at two operating modes: Mode 6 (4.2 bar BMEP, 2300 RPM) and Mode 11 (2.62 bar BMEP, 1500 RPM). We wanted to evaluate the effect on emissions of operating the engine at low power (near idle) in conjunction with the low NOx strategy. Specifically, we report on emissions of total hydrocarbon (HC), carbon monoxide (CO), NOx, particulates (PM), formaldehyde, acetaldehyde, benzene, 1,3-butadiene, gas phase polyaromatic hydrocarbons (PAH's) and particle phase PAH's from a DaimlerChrysler OM611 CIDI engine using a low NOx engine operating strategy at Mode 22 (1.0 bar BMEP and 1500 RPM).

A previous paper reported (SAE Paper 2002-01-2884) that it was possible to decrease mode-weighted NOx emissions compared to the OEM calibration with corresponding increases in particulate matter (PM) emissions. These PM emission increases were partially overcome with the use of oxygenated diesel fuel additives. We wanted to know if compounds of toxicological concern were emitted more or less using oxygenated diesel fuel additives that were used in conjunction with a modified engine operating strategy to lower engine-out NOx emissions. Emissions of toxicologically relevant compounds from fuels containing triproplyene glycol monomethyl ether and dibutyl maleate were the same or lower compared to a low sulfur fuel (15 ppm sulfur) even under engine operating conditions designed to lower engine-out NOx emissions.