1996 Volume 31 Issue 10 Pages 764-774
The control of soot emission from the diesel engine have been one of the important subjects because the soot plays an important role in relation to air pollution.
The measuring of soot concentration on real time is not well established. Considerable understanding of soot concentration have been achieved by the measurements of mass concentration of soot from diesel engines by means of probe sampling methods (JIS type etc.) . Developments of the optical measuring system, in order to get a more detailed understanding of soot concentration in exhaust tube on real time, come up as an important problem.
The form of soot particles in the exhaust tube seems to be monodispersive and spherical or clusterlike, such as long chain polymer molecules. It assume that the form and number density of soot particles become a state of volume mean diameter.
This system have been made using the laser-light scattering and attenuation techniques by the G. Mie's theory to make clear the diameter and number density of soot particles. A50 (mW) helium-neon laser emitting monochromatic radiation at a wavelength of 632.8 (nm) is used as the light source. An incident light beam from the light source is composite beam of the vertical (i1) and horizontal (i2) polarization components.
The diameter of soot particle can be determined from the intensities ratio of both integral scattered light from soot particles.
i is the intensity of the scattered light. It's value is defined as [60°∫40° (i1+i2) dθ/140°∫120° (i1+i2) dθ], θis the scattring angle. The soot refractive index of m=1.85-I⋅0.475 proposed by Lee and Tien is selected, mass per unit volume of soot is assumed ρs=2.0 (g/m3)
The results are as follows. At fuel flow is 0.75 (LN/min), The volume mean diameter (Ds) of soot particles in the exhaust tube lie between 200 and 230 (nm) . The total mean diameter is about 214 (nm) .
The number density and mass concentration of soot particles are estimated to be about 1.90×106 (particles/cm3) and 0.02 (g/m3), respectively. The mass concentration is no significant difference between the results of optical method and filter system.
