Modelling a Gasoline Compression Ignition (GCI) Engine Concept 2014-01-1305

Future engines and vehicles will be required to reduce both regulated and CO₂ emissions. To achieve this performance, they will be configured with advanced hardware and engine control technology that will enable their operation on a broader range of fuel properties than today.

Previous work has shown that an advanced compression ignition bench engine can operate successfully on a European market gasoline over a range of speed/load conditions while achieving diesel-like engine efficiency and acceptable regulated emissions and noise levels. Stable Gasoline CI (GCI) combustion using a European market gasoline was achieved at high to medium engine loads but combustion at lower loads was very sensitive to EGR rates, leading to longer ignition delays and a steep cylinder pressure rise. In general, the simultaneous optimisation of engine-out emissions and combustion noise was a considerable challenge and the engine could not be operated successfully at lower load conditions without an unrealistic amount of boost pressure.

To identify ways to improve the lower load performance of a GCI engine concept, Computational Fluid Dynamics and KIVA simulations have now been completed on the same single cylinder bench engine configuration operating on market gasoline. This modelling has shown that Variable Valve Timing offers considerable potential for increasing the temperature inside the combustion chamber and reducing the ignition delay. The simulations have also identified the preferred placement of combustion assistance, such as a glow plug, to extend the operating range and performance on gasoline, especially under the lowest load and cold engine starting conditions.