Experimental and Computational Investigation of PAH Production in a Diesel Engine as a Function of Load 2006-01-1977

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 experimental data was obtained for napthalene, phenanthrene, acenaphthylene, anthracene, acenaphthene, fluoranthrene, fluorene, and pyrene. Model calculations were carried out for prediction of the exhaust components: benzene, naphthalene, phenanthrene and pyrene under relevant engine operating conditions. Then for the two common PAHs, comparisons were made between the data and model results; for naphthalene and phenanthrene, comparisons were good. Both data and model showed that as load decreases (leaner combustion), the production of PAHs increases.