Particle Formation and Models

Abstract

This chapter reviews work on aerosols originating from internal combustion engines with an emphasis on soot formation during combustion as well as formation of semi‐volatile and ash particles during combustion and subsequent cooling and dilution processes. Mathematical models of particle formation in engines and remaining modeling challenges are also discussed. Aerosols are formed during combustion in the cylinder, in the exhaust system, and after the tailpipe. Specific mechanisms include the injection of fuel, formation and oxidation of particles during combustion, exhaust gas recirculation (EGR), and condensation of semi‐volatiles. The role of fuels is discussed with respect to their ignition behavior as a consequence of mixture preparation in the cylinder and with respect to their sooting propensity. Models for the formation, growth, and oxidation of soot particles are presented and the most popular mathematical approaches for simulating particle emissions are introduced. Solid and semi‐volatile nucleation mode particles are also discussed in some detail. Key drivers in the formation of these particles are sulfur in the fuel and lubricating oil and metals in the lubricating oil. Particle emissions of different types of gasoline engines with and without aftertreatment are also discussed and compared with diesel engine emissions. Some of the shortcomings of the current models and future research areas are highlighted at the end.

Combustion characteristics and liquid-phase visualisation of single isolated diesel droplet with surface contaminated by soot particles

“…This suggests the availability of deposited soot to dilute the mixture and possibly the droplet in fuel spray. Kittelson and Kraft [14] discussed that some particles which re-enter the cylinder through exhaust gas recirculation (EGR) can survive the oxidation process upon entering and may act as a sponge and attached to other remaining fuel droplets, engine oil and soot particles. Also, soot typically forms in rich region of combustion chamber which is nucleated from vapor phase to solid phase [15].…”

Effects of Biodiesel Blends Varied by Cetane Numbers and Oxygen Contents on Stationary Diesel Engine Performance and Exhaust Emissions

“…SOF emissions are made up of condensed hydrocarbons embedded within the soot emissions in the form of very fine particles. The size distribution of PM concentration has three peaks: the nucleation peak, which includes all volatile hydrocarbons (D p <~30 nm), the accumulation mode (~30 nm< D p <~500 nm), and the coarse mode (~500 nm<D p <~10 μm) [88]. These emissions are more pronounced during starting and engine idling when engine temperatures are reportedly very low [89].…”

Model Guided Application for Investigating Particle Number (PN) Emissions in GDI Spark Ignition Engines

“…Detailed derivations from first principles and convergence studies have been published previously [15,16,17,18,19,20]. The SRM has been used in a variety of applications including the simulation of fuels [21], GDI engines [22,23,24,25,26], traditional compression ignition engines [27,28,29], homogeneous charge compression ignition engines [30,31,32,33], and particulate emissions [34,35,36].…”