Characterization of CR diesel exhaust by UV-visible extinction and scattering spectroscopy

Non-intrusive diagnostic techniques based on broadband (190-550 nm) extinction and scattering spectroscopy were applied at undiluted exhaust Common- Rail (CR) diesel engine in real time. The influence of load and Exhaust Gas Recirculation (EGR) on soot mass concentration, size distribution of emitted particles and NO concentration was analyzed. NO concentration was evaluated by ""in-situ"" ultraviolet-visible absorption measurements and compared with those obtained by conventional analyzer. The extinction and scattering spectra were compared with those evaluated by the Lorenz-Mie model for spherical particles in order to retrieve the size, the number concentration of the emitted particles and particulate mass. The optical measurements showed that new generation diesel engines, in spite of a drastic reduction of the exhaust mass concentration, caused the emission in the atmosphere of high number concentration of carbonaceous nanoparticles.