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A tool was developed by Illinois Tool Works (ITW) called the “AutoEKG®FSA” (AutoEKG Fuel System Analyzer) which evaluates combustion quality in an engine by measuring the exhaust pulses of the engine. While many factors are known to influence combustion quality and the wave pattern produced by the instrument, the primary factor in this study was the presence of an asphalt-like material in the air intake system. By examining the waveforms measured by the AutoEKGFSA system before and after carbon cleaning, it has been observed that the engines studied not only run better after the removal of carbon in the system, but the improvements may be measured using this system.

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).

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.