Search Results

To help predict hydrocarbon emissions during cold-start conditions we are developing a numerical model for the dynamics and vaporization of the liquid wall films formed in port-injected spark-ignition engines and incorporating this model in the KIVA-3 code for complex geometries. This paper summarizes the current status of our project and presents illustrative example calculations. The dynamics of the wall film is influenced by interactions with the impinging spray, the wall, and the gas flow near the wall. The spray influences the film through mass, tangential momentum, and energy addition. The wall affects the film through the no-slip boundary condition and heat transfer. The gas alters film dynamics through tangential stresses and heat and mass transfer in the gas boundary layers above the films. New wall functions are given to predict transport in the boundary layers above the vaporizing films.

We report extensions of a three-dimensional computational model for the liquid wall films formed in port-injected engines. The extensions incorporate effects associated with spray/wall interactions-including droplet splash, film spreading due to impingement forces, and motion due to film inertia. We also include a submodel for the effects of liquid expelled from valve seat areas when valves close. Implementation of the extensions in the KIVA-3V computer program is described, and results of KIVA calculations of open- and closed-valve injection in a realistic four-valve engine geometry are presented. Computed film locations agree qualitatively with those observed in laser-induced fluorescence measurements.

This paper summarizes a comprehensive numerical model that represents the spray dynamics, fluid flow, species transport, mixing, chemical reactions, and accompanying heat release that occur inside the cylinder of an internal combustion engine. The model is embodied in the KIVA computer code. The code calculates both two-dimensional (2D) and three-dimensional (3D) situations. It is an out-growth of the earlier 2D CONCHAS-SPRAY computer program. Sample numerical calculations are presented to indicate the level of detail that is available from these simulations. These calculations are for a direct injection stratified charge engine with swirl. Both a 2D and a 3D example are shown.