Soot Mass Concentration Measurements in Diesel Engine Exhaust Using Laser-Induced Incandescence

Simultaneous measurements of laser-induced incandescence (LII) and elastic scattering from soot particles in diesel engine exhaust have been made. The LII signal scaled linearly with the mass concentration of the non-volatile particulate mass fraction over the entire range of engine operating loads. Over this range of conditions, the volume mean diameter of the soot particles varied from 0.07 to 0.11 μm, but the size change did not appear to affect the signal response. The scattering response did not scale linearly with the mass concentration of soot. Mass concentrations of 0.2 mg/m3 were easily detectable, with even lower values possible. Additional techniques for determining the volatile fraction of particulate mass are described.