Load Range Extension in Gasoline/Diesel Dual-Fuel Engines: A Mixture Concentration and Reactivity Control Approach

Abstract

Abstract. In gasoline/diesel dual-fuel engines, regulating fuel concentration and reactivity stratification effectively extends the high-load limit. This study investigates the effects of mixing characteristics of low- and high-reactivity fuels on combustion and emission performance. Based on intake airflow characteristics, an asymmetric port fuel injection strategy is proposed to control gasoline concentration stratification. Results show that forming local fuel-rich zones (equivalence ratio > 0.6) in the near-wall area significantly reduces total hydrocarbons and carbon monoxide emissions. Experimental and numerical analyses reveal that advancing diesel injection timing enhances chemical reactivity in the boundary zones while suppressing high-temperature oxidation in the core zones. Specifically, advancing the injection timing from 20 to 40 crank angle degrees before top dead center improves brake thermal efficiency by 1.5% and reduces total hydrocarbons, carbon monoxide, and nitrogen oxides emissions by 22.90%, 15.91%, and 40.60%, respectively. Late diesel injection offers greater flexibility in combustion phasing control. With the diesel double-injection strategy, a 90% gasoline substitution ratio achieves 43.57% brake thermal efficiency at 1.0-MPa brake mean effective pressure. At 1.5-MPa brake mean effective pressure, a 75% gasoline substitution ratio achieves 44.13% brake thermal efficiency, with emissions of 1.58, 5.76, and 1.88 g/kWh of total hydrocarbons, carbon monoxide, and nitrogen oxides, respectively.