Numerical Parametric Study of a Six-Stroke Gasoline Compression Ignition (GCI) Engine Combustion- Part II

In order to extend the operability limit of the gasoline compression ignition (GCI) engine, as an avenue for low temperature combustion (LTC) regime, the effects of parametric variations of engine operating conditions on the performance of six-stroke GCI (6S-GCI) engine cycle are numerically investigated, using an in-house 3D CFD code coupled with high-fidelity physical sub-models along with the Chemkin library. The combustion and emissions were calculated using a skeletal chemical kinetics mechanism for a 14-component gasoline surrogate fuel. Authors' previous study highlighted the effects of the variation of injection timing and split ratio on the overall performance of the 6S-GCI engine and the unique mixing-controlled burning mode of the charge mixtures during the two additional strokes. As a continuing effort, the present study details the parametric studies of initial gas temperature, boost pressure, fuel injection pressure, compression ratio, and EGR ratio. The focus of this paper is on the impact of these parameters on the performance of the two additional strokes of the 6S-GCI cycle such that the extent of controllability of ignition, combustion, and energy recovery processes can be understood. The results advocate possible methods of expanding the operating conditions for GCI combustion by governing the mixture stratification and thermal conditions of the charge mixtures. In an effort to understand the underlying physics of the mixing-controlled mode of combustion, Spray combustion in a constant volume combustion chamber (CVCC) was investigated with various thermal and chemical conditions of the charge mixtures that represent the in-cylinder conditions formed during the last two strokes. The emphasis of the analysis was on characterizing the soot formation/oxidation processes in gasoline spray combustion.