Achieving Stable Engine Operation of Gasoline Compression Ignition Using 87 AKI Gasoline Down to Idle

For several years there has been a great deal of effort made in researching ways to run a compression ignition engine with simultaneously high efficiency and low emissions. Recently much of this focus has been dedicated to using gasoline-like fuels that are more volatile and less reactive than conventional diesel fuel to allow the combustion to be more premixed. One of the key challenges to using fuels with such properties in a compression ignition engine is stable engine operation at low loads. This paper provides an analysis of how stable gasoline compression ignition (GCI) engine operation was achieved down to idle speed and load on a multi-cylinder compression ignition engine using only 87 anti-knock index (AKI) gasoline. The variables explored to extend stable engine operation to idle included: uncooled exhaust gas recirculation (EGR), injection timing, injection pressure, and injector nozzle geometry. The results of three-dimensional computational fluid dynamics engine combustion simulations revealed the importance of retaining sufficient local richness and stratification of the fuel-air mixture centered in the piston bowl for stable ignition and combustion at idle operation. By updating the low speed and load engine fuel consumption data, Autonomie vehicle simulations predicted an improved advantage of GCI engine operation compared to baseline port fuel injection gasoline engine operation from 25% to 28.7%.