In this paper, two different optical techniques for detection, sizing and counting nanoparticles were used at the undiluted exhaust of diesel engine: Broadband Ultraviolet-Visible Extinction and Scattering Spectroscopy (BUVESS) and Laser Induced Incandescence (LII). They are powerful "in situ" and non intrusive techniques for the study of PM in terms of mass concentration, size of particles and chemical properties. BUVESS overcomes intrinsic limitations of single wavelength techniques by using the data at several wavelengths to retrieve particle size distribution with better accuracy and moreover, the analysis of spectral scattering and extinction features may give information about particulate chemical nature and characterize the physical structure. On the other side LII allows measuring mean size of primary particles with a large measurement range, not limited by aggregate size. Both optical techniques were applied at undiluted exhaust of 16 v - 1.9 l Common Rail (CR) diesel engine. Measurements were carried out upstream and downstream Catalyzed Diesel Particulate Filter (CDPF). Different engine operating conditions were selected in order to evaluate dynamic range of the techniques for low-mass particulate emission. The mean diameters resulted from BUVESS and LII measurements were compared with those obtained by Electrical Low Pressure Impactor (ELPI) and Transmission Electronic Microscopy (TEM). According to BUVESS results, the size distribution was characterized by two classes of high number concentrations ultrafine particles. In the nucleation mode the mean size of particles was about 15 nm and less than 100 nm in the accumulation one. A significant difference between ELPI and BUVESS size distributions was observed in nucleation mode indicating the capability of optical technique to measure nanoparticles . On the other hand, in the overlapping size range number concentration resulted in good agreement. Moreover, ELPI mean diameters were bigger than those measured by LII and BUVESS and TEM . These results were due to the fact that BUVESS, LII and TEM methods probably measured primary particles; meanwhile ELPI did not discriminate between primary particle or aggregate. ELPI was more efficient for fine and coarse particles with respect to ultrafine ones. Wide characterization of downstream CDPF exhaust was performed. BUVESS and LII measurements showed higher sensitivity than ELPI for nucleation with respect to accumulation particles. In particular, the filtering induced by CDPF decreased nucleation mean diameter less than 10 nm and had higher efficiency on accumulation mode.
Nanoparticles detection at the exhaust of a common rail Diesel engine by different methodologies
Vaglieco BM;Merola SS
2005
Abstract
In this paper, two different optical techniques for detection, sizing and counting nanoparticles were used at the undiluted exhaust of diesel engine: Broadband Ultraviolet-Visible Extinction and Scattering Spectroscopy (BUVESS) and Laser Induced Incandescence (LII). They are powerful "in situ" and non intrusive techniques for the study of PM in terms of mass concentration, size of particles and chemical properties. BUVESS overcomes intrinsic limitations of single wavelength techniques by using the data at several wavelengths to retrieve particle size distribution with better accuracy and moreover, the analysis of spectral scattering and extinction features may give information about particulate chemical nature and characterize the physical structure. On the other side LII allows measuring mean size of primary particles with a large measurement range, not limited by aggregate size. Both optical techniques were applied at undiluted exhaust of 16 v - 1.9 l Common Rail (CR) diesel engine. Measurements were carried out upstream and downstream Catalyzed Diesel Particulate Filter (CDPF). Different engine operating conditions were selected in order to evaluate dynamic range of the techniques for low-mass particulate emission. The mean diameters resulted from BUVESS and LII measurements were compared with those obtained by Electrical Low Pressure Impactor (ELPI) and Transmission Electronic Microscopy (TEM). According to BUVESS results, the size distribution was characterized by two classes of high number concentrations ultrafine particles. In the nucleation mode the mean size of particles was about 15 nm and less than 100 nm in the accumulation one. A significant difference between ELPI and BUVESS size distributions was observed in nucleation mode indicating the capability of optical technique to measure nanoparticles . On the other hand, in the overlapping size range number concentration resulted in good agreement. Moreover, ELPI mean diameters were bigger than those measured by LII and BUVESS and TEM . These results were due to the fact that BUVESS, LII and TEM methods probably measured primary particles; meanwhile ELPI did not discriminate between primary particle or aggregate. ELPI was more efficient for fine and coarse particles with respect to ultrafine ones. Wide characterization of downstream CDPF exhaust was performed. BUVESS and LII measurements showed higher sensitivity than ELPI for nucleation with respect to accumulation particles. In particular, the filtering induced by CDPF decreased nucleation mean diameter less than 10 nm and had higher efficiency on accumulation mode.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
