Investigations on Soot Emission Behavior of A Common-Rail Diesel Engine during Steady and Non-Steady Operating Conditions by Means of Several Measuring Techniques

In this work the influence of various engine load changes with different engine speeds on the soot particle concentrations and properties was investigated because these operating modes are well known for short but high soot emissions. To derive specific information on emission behavior of particle matters tests were carried out with the Two-Color-Method and the so called RAYLIX technique in a four-cylinder CR-Diesel engine.

The Two-Color-Method (2CM) gives crank angle resolved information about soot formation and oxidation processes inside the combustion chamber of a single cylinder.

The RAYLIX technique is a combination of Rayleigh-scattering, Laser-Induced-Incandescence (LII) and extinction measurements which enable simultaneous measurements of temporally and spatially resolved soot concentration, mean primary particle radii and number densities in the exhaust gas manifold of the same cylinder investigated by the Two-Color-Method. A laser light sheet was launched into an optical flange mounted between the cylinder head and the exhaust manifold. Both signals were detected by two intensified CCD cameras. Additionally, measurements of the opacity and the Filter Smoke Number were performed in the exhaust gas.

The results of the time resolved measuring techniques 2CM and RAYLIX were correlated with results obtained by the conventional methods in the exhaust gas. During most load changes under investigation temporary higher soot concentrations inside the combustion chamber as well as in the exhaust gas could be found compared to those measured in the stationary engine operation points before and after the load changes. This increase was observed even though the simultaneously measured mean primary particle sizes showed a decreasing behavior. This decrease was overcompensated by a disproportionate increase in the particle number density.