CFD Modeling of a Vortex Induced Stratification Combustion (VISC) System

This paper describes the CFD modeling work conducted for the development and research of a Vortex Induced Stratification Combustion (VISC) system that demonstrated superior fuel economy benefits. The Ford in-house CFD code and simulation methodology were employed. In the VISC concept a vortex forms on the outside of the wide cone angle spray and transports fuel vapor from the spray to the spark plug gap. A spray model for an outward-opening pintle injector used in the engine was developed, tested, and implemented in the code. Modeling proved to be effective for design optimization and analysis. The CFD simulations revealed important physical phenomena associated with the spray-guided combustion system mixing preparation. This paper presents the effect of various parameters such as piston shape, injector axial position, spark plug axial position, swirl control valve (SCV), exhaust gas recirculation (EGR) on mixture formation that affects the combustion, misfire rate, and stability in stratified-charge operation. A smoke correlation based on the amount of piston wetting and the amount of vapor in the rich regions will also be presented together with the effect of the piston shape, manifold absolute pressure (MAP), and split injection on smoke emissions in stratified-charge operation. The mixture preparation in homogeneous-charge operation in the current VISC system with a centrally mounted injector will be compared to the mixture preparation in a wall-guided system with a side-mounted injector.