An assessment of how distance and diesel oxidation catalyst will impact thermal decomposition behaviors of particles

Decomposition mass loss and pyrolysis products analyses of particles sampled at various locations along the tailpipe of a Euro-IV diesel engine were performed using a thermo gravimetry in conjunction with Fourier transformation infrared spectrometrymass spectrum.Diesel particles were collected at the same location with and without diesel oxidation catalyst(DOC)mounted on the test engine separately.The three poles in thermal gravity-differential thermal gravity images suggested that the decomposition process of diesel particles could be divided into three stages which correspond to the decompositions of lower boiling substances,higher boiling substances and soot respectively.It is noticed that no matter whether DOC was mounted or not,the further the particles were sampled away from the engine block,the lower the peak temperatures and the heavier the mass losses within the first two stages,which indicated that the soluble organic fraction in the particle samples increased and therefore lowering the activation energy of thermal decomposition.Hydroxyl,ammonia,C_xH_y fragments,benzene,toluene,and phenol were found to be the primary products of particle decomposition,which didn’t change with the location of particle sample point.The employment of DOC increased the activation energy for particle oxidation and resulted in a higher peak temperature and lower mass loss within the first-stage.Moreover,the C=O stretching bands of aldehyde and ketone at 1771 cm-1 was only detected without a DOC,while the N02 peak at 1634 cm-1 was solely noticed with the presence of DOC.Compared to the first-stage pyrolysis products,more polycyclic aromatic hydrocarbons and less C_xH_y fragments were seen in the second-stage.

On-board measurement of particle numbers and their size distribution from a light-duty diesel vehicle:Influences of VSP and altitude

In this study,the particle size-resolved distribution from a China-3 certificated light-duty diesel vehicle was measured by using a portable emission measurement system（PEMS）.In order to examine the influences of vehicle specific power（VSP） and high-altitude operation,measurements were conducted at 8 constant speeds,which ranged from 10 to 80 km/hr at10 km/hr intervals,and two different high altitudes,namely 2200 and 3200 m.The results demonstrated that the numbers of particles in all size ranges decreased significantly as VSP increased when the test vehicle was running at lower speeds（〈 20 km/hr）,while at a moderate speed（between 30 and 60 km/hr）,the particle number was statistically insensitive to increase VSP.Under high-speed cruising conditions,the numbers of ultrafine particles and PM2.5were insensitive to changes in VSP,but the numbers of nanoparticles and PM10 surged considerably.An increase in the operational altitude of the test vehicle resulted in increased particle number emissions at low and high driving speeds;however,particle numbers obtained at moderate speeds decreased as altitude rose.When the test vehicle was running at moderate speeds,particle numbers measured at the two altitudes were very close,except for comparatively higher number concentrations of nanoparticles measured at 2200 m.