Synthetic GTL e-diesel as high-reactivity fuel for RCCI/MMDF heavy-duty combustion

The decarbonization of medium- and heavy-duty transport requires advanced combustion strategies capable of simultaneously reducing greenhouse gas emissions and pollutant formation while maintaining high efficiency under both steady-state and transient operation. In this context, Multi-Mode Dual-Fuel combustion has demonstrated strong potential for ultra-low NOx and soot emissions; however, the use of conventional diesel as the high-reactivity fuel limits its overall carbon reduction potential. This work experimentally evaluates the use of synthetic GTL e-diesel as high-reactivity fuel in a 7.7 L heavy-duty dual-fuel engine operating with gasoline as low-reactivity fuel under Multi-Mode Dual-Fuel combustion. The study includes a direct fuel substitution assessment, a dedicated full-map recalibration, and validation under the World Harmonized Stationary Cycle. The baseline comparison showed that GTL e-diesel advanced combustion phasing at low and medium loads, increasing brake thermal efficiency by approximately 1–2% in selected operating regions. GTL also reduced soot, CO, and HC emissions across most of the engine map, although NOx penalties appeared at low loads due to earlier combustion. A dedicated calibration based on air-path and injection optimization successfully restored EURO VI compliance over a broader operating region while preserving efficiency benefits. During World Harmonized Stationary Cycle operation, the optimized GTL configuration maintained stable combustion and reduced cycle-integrated NOx, soot, fuel consumption, CO, and HC emissions relative to diesel Multi-Mode Dual-Fuel combustion. Furthermore, Well-to-Wheel analysis showed approximately 20% lower CO₂ emissions compared to diesel operation, demonstrating the carbon reduction potential of GTL e-diesel in dual-fuel heavy-duty engines.