Estimation of semi-volatile particle composition from premixed low temperature Diesel combustion using evaporative tandem differential mobility analysis

Diesel low temperature combustion (LTC) is an engine operational strategy that effectively reduces soot and oxides of nitrogen (NOx) emissions. A downside to LTC is particulate matter (PM) containing high levels of semi-volatile material due to elevated hydrocarbon concentrations. The mechanics of formation and composition of this semi-volatile PM has been largely uncharacterized. In this work, we investigate engine-out PM and HC emissions from LTC modes and equivalent conventional diesel combustion modes. An experimental strategy using tandem differential mobility analysis was implemented to investigate organic PM volatility as a function of particle size. The results indicate that semi-volatile PM from LTC is comprised of compounds spanning a wide range of volatilities. Differences in PM volatility were even greater for particles of different size groups. The results show that gas-to-PM conversion processes require additional investigation to determine the clear impact of LTC implementation on real-world PM emissions.