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The optimization of combustion system of a single-cylinder d.i. diesel engine, representative of heavy-duty family, is discussed. The characterization of in-cylinder fluid motion of a conventional straight-sided and a re-entrant combustion chamber, carried out by LDA technique, is presented. Engine tests, using the same chambers and sacless nozzles with different holes diameter and appropriate spray angle, have been performed. Strong reduction of smoke and HC emissions has been obtained, remaining unchanged the engine performance.

Improvement of combustion system for low emissions of a single cylinder diesel engine is presented. In particular the effects of spray angle, holes diameter and number, compression ratio and combustion chamber geometry on engine performance and emissions are evaluated. The fluid-dynamic behaviour of combustion system is analyzed by LDA technique. Engine tests have been carried out at two engine speed and at different start of combustion. The particulate matter has been analyzed in terms of soluble organic fraction and dry soot.

Cycle resolved LDA measurements of the tangential velocity component, made along a diameter of two combustion chambers (toroidal and square) during the compression stroke of a diesel engine operating at 600 and 1000 rpm, are discussed. Indirect measurements of lateral integral length scales determined by single point autocorrelation technique are presented. Finally direct measurements of lateral integral length scales made by a new laser doppler velocimeter system based on two probe volume technique are reported.