New trends in combustion system design of light duty Diesel engines inferred by threedimensional C.F.D. computations

In the present paper some results, obtained by the use of modern numerical C.F.D. tools, are presented. In particular, starting from the experimental characterization of a conventional design D.I. diesel engine, the empirical constants of the different submodels were tuned to obtain satisfactory results in some key test conditions. After that, in the same points of the engine performance map, the following parameters were systematically varied: fuel injection system design and operating conditions; intake swirl level; exhaust gas recirculation level. The influence of each parameter on combustion evolution is discussed and the most promising trend for the engine optimization is presented. Taking into account the model formulations limits, the results obtained suggest, from a theoretical point of view, that "common rail" equipped light duty diesel engines are suitable to meet the future European emission regulations. In particular the numerical analysis demonstrate that the emission potential of common rail engines is positioned between 2001 and 2005 emission limits. The last stage of emission regulations can be achieved only with further massive research activities.