Modeling the Combustion in a Small-Bore Diesel Engine Using a Method Based on Representative Interactive Flamelets

A model based on Representative Interactive Flamelets (RIF) for simulating ignition, combustion and emissions formation in a DI diesel engine has been applied to describe the combustion process in the Ford DIATA engine. Equipped with a common-rail injection system the four-valve, turbocharged engine with a displacement of 300 cc per cylinder represents a modern HSDI small-bore diesel engine. The RIF-model offers a way of decoupling the turbulent time scales from those associated with the chemistry. The turbulent flow field was solved using the three-dimensional CFD-code KIVA 3V and the chemistry was solved in a one-dimensional flamelet code rendering profiles of species mass fractions as a function of the mixture fraction, which is a conserved scalar. This decoupling enabled a detailed reaction mechanism comprising 118 species and 557 elementary reactions to be employed without imposing a significant penalty on the computational time. Model predictions of crank angle resolved in-cylinder pressure and NO_x emissions are compared with experimental data taken from a single-cylinder test engine varying injection timing and EGR. The agreement between simulations and experiments is found to be very good.