Development and Analysis of a Spray-Guided DISI Combustion System Concept 2003-01-3105
An innovative stratified-charge DISI combustion concept has been developed using a mixture formation method referred to as Vortex Induced Stratification Combustion (VISC). This paper describes the combustion system concept and an initial assessment of it, performed on a single-cylinder test engine and through CFD modeling. This VISC concept utilizes the vortex naturally formed on the outside of a wide spray cone that is enhanced by bulk gas flow control and piston crown design. This vortex transports fuel vapor from the spray cone to the spark gap. This system allows a late injection timing and produces a well-confined mixture, which together provide an improved compromise between combustion phasing and combustion efficiency over typical wall-guided systems. Testing results indicate an 18% fuel consumption reduction, compared with a baseline PFI engine, over a drive cycle (neglecting cold start and transient effects). This represents a 4-7% reduction in fuel consumption compared with previous in-house stratified-charge DISI concepts, while providing similar stability and emissions performance. These benefits are shown to arise from improved combustion phasing, reduced unburned hydrocarbon emissions, and an enlarged window of stratified operation. In addition, the potential use of split injection to expand the window of stratified operation to higher loads is outlined. Potential for improved full-load performance is also shown due to improved air-fuel mixing.