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Exhaust gas recirculation (EGR) coolers experience degradation of performance as a result of the buildup of material in the gas-side flow paths of the cooler. This material forms a deposit layer that is less thermally conductive than the stainless steel of the tube enclosing the gas, resulting in lower heat exchanger effectiveness. Biodiesel fuel has a fuel chemistry that is much more susceptible to polymerization than that of typical diesel fuels and may exacerbate deposit formation in EGR coolers. A study was undertaken to examine the fundamentals of EGR cooler deposit formation by using surrogate tubes to represent the EGR cooler. These tubes were exposed to engine exhaust in a controlled manner to assess their effectiveness, deposit mass, and deposit hydrocarbon content. The tubes were exposed to exhaust for varying lengths of time and for varying coolant temperatures. The results show that measurable differences in the response variables occur within a few hours.

A single cylinder engine was operated in HCCI mode with diesel-range fuels, spanning a range in cetane number (CN) from 34 to 62. In addition to measurements of standard gaseous emissions (CO, HC, and NOx), multiple sampling and analysis techniques were used to identify and measure the individual exhaust HC species including an array of oxygenated compounds. A new analytical method, using liquid chromatography (LC) with electrospray ionization-mass spectrometry (ESI-MS) in tandem with ultraviolet (UV) detection, was developed to analyze the longer chain aldehydes as well as carboxylic acids. Results showed an abundance of formic and butyric acid formation at or near the same concentration levels as formaldehyde and other aldehydes.

This paper reports the test results from the DPF (diesel particulate filter) portion of the DECSE (Diesel Emission Control - Sulfur Effects) Phase 1 test program. The DECSE program is a joint government and industry program to study the impact of diesel fuel sulfur level on aftertreatment devices. A systematic investigation was conducted to study the effects of diesel fuel sulfur level on (1) the emissions performance and (2) the regeneration behavior of a continuously regenerating diesel particulate filter and a catalyzed diesel particulate filter. The tests were conducted on a Caterpillar 3126 engine with nominal fuel sulfur levels of 3 parts per million (ppm), 30 ppm, 150 ppm and 350 ppm.