Study of Effects of Fuels and After-Treatment Systems on Formation Process of Particles from Diesel Engines

Abstract

Diesel engines have good potential for improved fuel economy, owing to their high thermal efficiency and fuel diversity. Diesel engines have been developed to address global warming and improve air quality and health around the world. Although particles produced by combustion in the cylinders of a diesel engine are emitted into the atmosphere, they can be dramatically reduced by over 99.9% after being trapped by a diesel particulate filter (DPF) and through the use of a diesel oxidation catalyst (DOC) in after-treatment systems. However, the mechanism of the formation of these particles in the cylinders and the exhaust behaviors of the particles after being trapped by the DPF have not yet been clearly explained and the effects of a DOC on the formation of these particles are still not clarified. Thus, this study analyzes particle distributions, particle number, particle components, and exhaust time behavior from an after-treatment system to atmosphere, using JIS2 diesel and biodiesel fuel (BDF). This paper reveals how particles are trapped by a DPF equipped on a diesel engine and emitted through the DPF to the atmosphere, based on detailed measurements of the number of particles. Particle size distributions are analyzed for two DPF types, SiC and cordierite. The effects of the DOC on the formation and exhaust behavior of particles for each type of DPF are also described. This paper presents photographs of particles generated by combustion of JIS2 diesel fuel and BDF and of particles in the tail pipe following an after-treatment system with a DOC and DPF. This paper also shows the diameters of single particles and sizes of aggregated particles exhausted from a diesel engine and emitted following an after-treatment system. Finally, this study proposes a formation process for particles produced by combustion in the cylinders of a diesel engine and emitted following an after-treatment system.