Search Results

The technique of liquid Water Injection (WI) at the intake port of downsized boosted SI engines is a promising solution to improve the knock resistance at high loads. In this work, an existing 1D engine model has been extended to improve its ability to simulate the effects of the water injection on the flame propagation speed and knock onset. The new features of the 1D model include an improved treatment of the heat subtracted by the water evaporation, a newly developed correlation for the laminar flame speed, explicitly considering the amount of water in the unburned mixture, and a more detailed kinetic mechanism to predict the auto-ignition characteristics of fuel/air/water mixture. The extended 1D model is validated against experimental data collected at different engine speeds and loads, including knock-limited operation, for a twin-cylinder turbocharged SI engine.

A multi-zone model for the prediction of performance and emissions of indirect injection diesel engines is presented. The interaction between turbulent mixing and chemical reaction, which primarily controls combustion, is described as a stochastic process by means of a Monte Carlo collision-dispersion model. The major contribution of the present work lies in combining such an approach with improved models of fuel evaporation in supercritical conditions, burning rate, radiative heat transfer and flow coefficient of the passageway, besides properly accounting for the real gas effects. A limited number of empirical correlations was introduced, so obtaining a rather general and physically meaningful predictive tool. Experimental data concerning a small single-cylinder engine have been employed to validate the computational procedure.