Study on combustion and emissions of methanol engines based on active pre-chamber jet ignition technology

Against the backdrop of the ''dual carbon'' goals, this study addressed the challenges of narrow lean-burn limits and low thermal efficiency in conventional spark-ignition (SI) methanol engines by proposing the active pre-chamber jet ignition (APCH-JI) technology. A combined approach of engine bench testing and three-dimensional computational fluid dynamics (CFD) simulations using CONVERGE software was employed to systematically investigate its performance characteristics. A prechamber (PC) structure was designed to achieve uniform distribution of the in-cylinder mixture by comparing spray angles and injection timing of different injectors, thereby obtaining optimal ignition performance. Compared to SI, APCH-JI significantly shortened the combustion duration, reducing the 90 % combustion phase (CA90) by 32 %. Under lean-burn conditions, APCH-JI enabled stable combustion, increasing indicated thermal efficiency (ITE) by 4 % to a maximum of 47.2 % at a maximum air-fuel ratio (λ) of 2.1, while reducing indicated fuel consumption by 8 %–12 %. Concurrently, emissions of nitrogen oxides (NOx), hydrocarbons (HC), and carbon monoxide (CO) were synergistically reduced. This study provides a viable technical pathway for the efficient and clean operation of methanol engines.