Abstract
Although the direct injection gasoline engine offers the potential for large fuel consumption reductions in passenger vehicles, the wide spread adoption of this technology has been slow. With the onset of ever increasingly stringent emissions legislation requiring the reduction of exhaust pollutants, the DI combustion system for the future must therefore exhibit the favourable combination of significant fuel consumption reduction with low engine emissions levels in a vehicle environment. The spray guided combustion system has been shown to provide perhaps the best potential to deliver the fuel consumption reduction and low emissions levels required of the advanced concepts, but must overcome shortfalls of reportedly high sensitivity to operating parameters including injection and ignition timing. The Orbital air-assisted fuel system has unique properties in the manner in which the fuel is delivered into the combustion chamber, specifically the time varying flow rate of fuel injected during the direct injection event. By managing this instantaneous fuel flow rate through the direct injector, it is shown that the air-assisted system, when applied to a spray guided combustion system, has the ability to achieve low fuel consumption and emissions levels, combined with reduced sensitivity to variation in ignition and injection timings to achieve a robust combustion system.