Combustion Mechanism Analysis with In-Chamber Gas Composition Measurements in a Premixed Lean Compression Ignition Engine.

The in-chamber and exhaust gases from a premixed lean compression ignition engine were evaluated with high-speed direct gas sampling and gas chromatography. The results showed that in a premixed lean CI engine the in-chamber concentrations of THC and CO were always much higher than in conventional diesel combustion and remained nearly constant after the main part of the heat release was finished. The THC near the piston cavity wall was much higher than the the center of the combustion chamber and near the cylinder head. Deposition of fuel on the piston face was proved to be the main reason for higher THC emissions from premixed lean CI engine. The experiments with the model fuels showed that during combustion amounts of unburnt hydrocarbon components with lower boiling points decreased more than higher boiling point components, while there was little difference in the relative fractional amounts based on component ignitability.