Soot formation during benzene pyrolysis is of interest due to use of fuels with increased aromatic content resulting in high level of particulate emissions from vehicular exhausts,furnaces,and manufacturing processes relatively to those emissions from low C/H ratio fuels.This work is aimed at video system investigation of charged soot aggregate formation due to benzene pyrolysis in reactor presented in Fig.1.A mixture of benzene with nitrogene is supplied to the input of reactor at atmospheric pressure and room temperature.The partial pressure of benzene in this mixture is 100 Torr.The experiments were carried out at the temperature in reaction zone of 1350 K.The imput flow rate is varied in the range qi=0.25-2.5 scc/s which corresponds to the residence time in reaction zone t=0.6-6 c.The pyrolysis of benzene resulted in soot aggregate formation (Fig.2).The size of aggregates is 0.1-1 jam,the mean size of primary particles about 100 nm.An imaging system was used for soot observations.To this aim,a small portion of aerosol was injected to an optical cell.Light of a He-Ne laser beam scattered by soot particles at an angle of 90deg passed through a flat window to a microscope objective and then to a CCD camera connected to a TV system.This optical setup resolves images of aggregates larger than about 3 jam;smaller aggregates were visible as spots.To create an electric field,two parallel electrodes were fixed in the cell at a distance of 0.25 cm.The velocity of aggregate movement in the electric field with intensity of 360 V/cm gave information on the electric charge of aggregates.We estimated the aggregate net charge from the balance between the Coulomb force and the drag force.The crucial point in these estimations was determination of equivalent radius of aggregate Rm.
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