Abstract
Diesel engine emissions have gained increased attention during the last two decades. Especially participate matter and volatile components absorbed on the particles surface, like polycyclic aromatic hydrocarbons (PAH) and sulfate components are suspected to cause serious health hazards. Therefore, future emission regulations are getting stricter and force the engine manufacturers to a drastic reduction of particle emission levels. Besides the limitation of the total mass emission different particle size classes may be differently weighted. More realistic test conditions, like transient test cycles have been demanded and exhibit severe deficiencies of current particle measurement techniques. Conventional measurement systems are particularly inapplicable for ultra low concentrations or the investigation of transient behavior. In this study, the performance of time-resolved laser-induced incandescence (TIRE-LII) as a favorable on-line measurement tool for soot investigation within the exhaust pipe of low emission engines is described in the form of a prototype soot sensor. Based on a theoretical model, a favorable laser-optical method to measure both the soot mass concentration and the primary particle size utilizing the thermal radiation of laser heated soot is demonstrated. Particularly, the potential of LII is demonstrated with the help of three medium duty diesel engines. Several operation points have been investigated to study the effect on the soot mass concentration and primary particle size by varying engine parameters like rail and boost pressure and injection timing. The measured mass concentration has partly been compared with the results of conventional measurement systems. Finally, some ESC-tests (European Stationary Cycle) and, furthermore, first transient tests have been performed.
