Experimental assessment of gasoline compression ignition at medium to full-load in a heavy-duty multi-cylinder diesel engine

Gasoline compression ignition (GCI) has shown the potential to produce diesel equivalent efficiency while achieving ultra-low oxides of nitrogen (NOx) and soot emissions. Nonetheless, mechanical constraints under high load conditions have limited its implementation. A partially premixed compression ignition (PPCI) - diffusion combustion strategy has been developed to satisfactorily enable high efficiency and clean high-load GCI operation. By utilizing the PPCI-diffusion combustion strategy, this investigation assessed GCI performance experimentally on a heavy-duty diesel engine. Fuel injection strategy (start of injection, split ratio, and injection pressure) and air-handling system boundary conditions were systematically studied as key parameters under medium-to-full load engine operation. Across different engine operating points, GCI optimized using a one-factor-at-a-time approach demonstrated diesel-like fuel efficiency and emissions compared to the diesel baseline over an engine-out NOx range of 2–7 g/kWh. A design of experiments (DoE) based injection strategy optimization was also conducted at the highest fuel efficiency point, targeting 2.8 g/kWh engine-out NOx. The sensitivity of GCI performance to the fuel injection strategy was thoroughly characterized. The optimized fuel injection strategy showed equivalent diesel efficiency with an enhanced NOx-smoke trade-off without exceeding the mechanical constraints on maximum pressure rise rate (MPPR) and peak cylinder pressure (PCP).