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Reduction of particulate emissions from diesel engine is an important theme from the view point of air pollution. Experiments were carried out using a four-stroke single cylinder direct-injection diesel engine. A new method to measure diesel particulates has been developed. Particulates were sampled with a freezing method just behind an exhaust valve and examined through a scanning electron microscope. Shape and structure of particulates and the size distributions are measured under wide operating conditions obtained with above method. The total mass of particulate emissions was measured using a dilution tunnel sampling system. The heat release processes were analyzed using indicator diagrams and the relation between burning condition and particulate emissions were discussed, after systematic experiments under constant revolution speed of 2000 r/min for several load and injection timing conditions.

The mixing process of fuel with the surroundings are necessary to verify combustion process and then to make a combustion model. In this study, a single shot of diesel spray is injected through either a constant pressure injection system or bypass type injection system which has the same characteristics as the one of an actual engine. Measurement are made on the gas velocity distribution around the spray and its time history using a hot wire anemometer. The gas flow direction is determined by the smoke tracer method. In this investigation the axial and radial distributions of entrainment air are determined, and also their time histories are observed. Radial distribution of the entrainment velocity can be shown ū(t) = CrA and the entrainment coefficient αe is estimated to be a volume between 0.2 ∼ 0.3.