CFD-3D Multi-Cycle Analysis on a New 2-Stroke HSDI Diesel Engine

The paper describes a CFD multidimensional and multi-cycle engine analysis applied to a novel 2-Stroke HSDI Diesel engine, under development since a few years at the University of Modena and Reggio Emilia. In particular, six operating conditions are considered, two of them at full load and four at partial. The simulation tool is STAR-CD, a commercial software extensively applied by the authors to HSDI Diesel engines. Furthermore, an experimental calibration of the combustion model has been performed and reported in this paper, carrying out CFD simulations on a reference Four Stroke HSDI Diesel engine. As expected, in the multi-cycle analysis a wide dependence of pollutants on trapped charge composition has been found. Much less relevant is the cycle-by-cycle variation in terms of performance parameters, such as trapped mass, IMEP, combustion efficiency, etc. For these parameters, 2 cycle are sufficient to reach a reasonable convergence, while for pollutants 3 or more cycles are required. Information from multi-cycle simulation has been used to refine a 1D engine cycle model, providing a prediction on engine performance at several operating conditions. In particular, the influence of the combustion sub-model has been investigated, comparing the results obtained by entering empirical heat release laws to the results provided by a combustion model refined through multi-cycle 3D simulations.