The purpose of this study was the characterization of the size distribution and the concentration of the particles emitted by diesel engines under various speed and load points, and different injection pressures. Fine and ultrafine particles emitted by modern diesel engines, in particular those with sizes below 100 nm, are of significant importance for the human health, since the latter are respirable and may have therefore negative effects. The investigations described in this paper provide an insight into the formation of soot particles in the combustion chamber and their number concentration and size distribution in the exhaust gas pipe. The experiments were performed on a single cylinder diesel engine. For the purpose of comparability to multi cylinder engines, the crankshaft drive, the liner, the piston and the cylinder head were based on a heavy duty production engine. The engine was operated with a common rail injection system which was controlled by an electronic control device that offered several degrees of freedom regarding number, duration and timing of the single injections. During the investigations the engine was operated at several speed and load points with and without pilot injection. The in-cylinder soot concentration was measured crank angle resolved with the two-color-method. The Filter-Smoke-Number (FSN) and the NOx concentration were determined in the exhaust gas. Furthermore the particle number and the particle size distribution were measured by means of a Scanning Mobility Particle Sizer (SMPS). The main focus of the experiments was on the investigation of the in-cylinder soot concentration and the particle size distribution running the engine at several injection pressures during different engine speed/load configurations. In order to obtain a potential correlation to common exhaust gas quantification methods, the Filter-Smoke-Number was measured simultaneously. The results of the experiments provide knowledge which is of eminent importance with respect to further diesel combustion development with regard to both the soot concentration and the soot particle properties.

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