Volatility Characterization Of Particle Emissions From Premixed Low Temperature Compression Ignition Combustion

Abstract

This thesis constitutes an extensive volatility characterization of particles from engines operating in two low temperature combustion (LTC) modes, partially premixed compression ignition (PPCI), and reactivity controlled compression ignition (RCCI). Low temperature combustion is of research interest because it offers the potential to reduce soot and oxides of nitrogen (NOx) while capitalizing on the inherently high efficiency of compression ignition engines. While particle emissions from conventional diesel combustion (CDC) have been extensively studied and characterized, particle emissions from LTC modes have been shown to be distinctly different, and demand investigation. These particles have been shown to be primarily organic material with small amounts of solid soot and ash, in contrast to particles from CDC that are primarily soot with small amounts of adsorbed organic material. In this work, advanced aerosol experimental techniques have been applied to characterize the volatility of these particles. The results have shown that their composition results in formation that is especially sensitive to dilution conditions. The experimental data have been used to develop aerosol simulations that identify formation mechanisms responsible for the unique volatility characteristics of LTC particle emissions. Particle volatility characteristics shown in the experiments suggest that heavy unburned oil and fuel alkanes contribute greatly to particle growth, forming the bulk of total particle volume. Further, elevated levels of lower molecular weight, low volatility organic compounds resulting from LTC may contribute to the inception of particles due to homogeneous nucleation; however, the results show that despite ultra-low fuel sulfur concentrations, heterogeneous nucleation of particles by sulfuric acid and water is most likely contributor to nucleation mode particle formation for LTC modes.