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The present work examines the correlation between PAH (Polycyclic Aromatic Hydrocarbon) formation and diesel engine load and the development of a corresponding reaction kinetics based model. The model developed simulates combustion using the partially stirred reactor model of Chemkin at conditions relevant to actual diesel engine operation, i.e. prescribed piston movement as a function of crank angle and adjustment of turbulence mixing intensity to match experimental cylinder pressure data. Experiments were carried out for determination of: 1) pressure-crank angle history, and 2) measurements of the polycyclic aromatic hydrocarbons in the exhaust at each load condition. PAHs were collected with soot from a filter in the engine exhaust, extracted using supercritical carbon dioxide and quantified using GC/MS/MS (Gas Chromatography, Tandem Mass Spectrometry).

This paper addresses some of the practical problems encountered in attempts to use the simple alcohols as alternate fuels in compression ignition (CI) engines for transportation. It is comprised of six sections: 1) the motivations for pursuit of the alcohols for transportation, 2) a brief review of several municipal buses trials in North American cities, 3) relevant literature which is cited to support a hypothesis, 4) the presentation of a hypothesis and solution, 5) some engine performance data to address an issue attendant to the proposed solution, and 6) conclusion. The solution proposes auto ignition of the fuel via intake air heating as a means to overcome the part load engine efficiency problems. However, in implementing this strategy for a direct injection engine, elevated noise has been observed for alcohol operation. This was concluded to be due to a very rapid pressure rise on ignition attendant to air preheating and the high compression ratio of this engine.

The focus of this work is to understand how diesel engines “wetstack.” Mainly through the work which will be discussed here, the root cause appears to be the presence of polycyclic aromatic hydrocarbons (PAHs) in the exhaust and accumulation on the small clearance between the exhaust valve stem and the valve guide. Experimental data which support this premise was obtained by operating an engine at no load and collecting exhaust soot particulate on a filter paper onto which PAHs were adsorbed. Supercritical carbon dioxide extraction was then used extract PAHs for analysis. The extract was processed by GC/MS to quantify PAHs. Because of the high unburned fuel carry-over at these operating conditions, it was necessary to use tandem MS to isolate each PAH from fuel carry-over in the spectra.