Particle and nanoparticle characterization at the exhaust of internal combustion engines

The aim of this work is the characterization of the emissions of exhaust particles in terms of number size distribution and chemical–physical properties. Laser-induced incandescence and broadband ultraviolet–visible extinction and scattering spectroscopy were used at the exhaust of a common-rail diesel engine and of a port fuel injection (PFI) spark ignition (SI) engine. The optical results were compared with size distributions obtained with an electrical low-pressure impactor and a scanning mobility particle sizer. Moreover, the fundamental engine parameters and the particulate mass and gas concentrations were measured using conventional instrumentation. With respect to the diesel engine, the effect of the exhaust after-treatment was investigated. The exhaust gas recirculation influenced the particle size distribution in terms of number concentration owing to the formation of accumulation mode particles. The catalysed diesel particulate filter strongly reduced the particle number concentration in the loading phase. Effects on the chemical nature of the particles were observed during the filter regeneration phase. With respect to the PFI SI engine, high number concentrations of nanoparticles (D < 50 nm) were measured for all the engine operating conditions. The chemical nature of the nanoparticles was investigated.