Effect of Injection Timing on Detailed Chemical Composition and Particulate Size Distributions of Diesel Exhaust

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Abstract
An experimental study was carried out to investigate the effects of fuel injection timing on detailed chemical composition and size distributions of diesel particulate matter (PM) and regulated gaseous emissions in a modern heavy-duty D.I. diesel engine. These measurements were made for two different diesel fuels: No. 2 diesel (Fuel A) and ultra low sulfur diesel (Fuel B). A single-cylinder 2.3-liter D.I. diesel engine equipped with an electronically controlled unit injection system was used in the experiments. PM measurements were made with an enhanced full-dilution tunnel system at the Engine Research Center (ERC) of the University of Wisconsin-Madison (UW-Madison) [1, 2]. The engine was run under 2 selected modes (25% and 75% loads at 1200 rpm) of the California Air Resources Board (CARB) 8-mode test cycle. Samples were collected on a series of Teflon and baked quartz fiber filters to evaluate mass loading, elemental and organic carbon (EC/OC), and sulfates (SO42-) for several injection timings with the two different fuel compositions. A scanning mobility particle sizer (SMPS) was used to measure particle number concentrations and size distributions in the residence time chamber (RTC). Results show that the advanced injection timing significantly affected detailed chemical composition and size distributions of the PM. The advanced injection timing significantly decreased EC and modestly decreased OC, particularly at the higher load (mode 6). The impact on OC with changing fuel composition and the fuel composition's effect on changes in OC with injection timing were negligible and statistically insignificant. Sulfates did not change with the injection timing and/or engine load for Fuel B, however, Fuel A showed significant variations in the sulfates with the injection timing and/or engine load.

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