Study on Cold Start of Methanol Direct Injection Engine Based on Laser Ignition

Methanol has garnered attention as a promising alternative fuel for marine engines due to its high octane number and superior knock resistance. However, methanol-fueled engines face cold-start challenges under low-temperature conditions. Laser ignition technology, an emerging ignition approach, shows potential to replace conventional spark ignition systems. This study investigates the effects of laser ignition on combustion and emission characteristics of direct-injection methanol engines based on methanol fuel combustion mechanisms using the AVL-Fire simulation platform, focusing on optimizing key parameters, including ignition energy, longitudinal depth, and lateral position, to provide theoretical support for efficient and clean combustion in marine medium-speed methanol engines. Key findings include an ignition energy threshold (60 mJ) for methanol combustion stability, with combustion parameters (peak pressure, heat release rate) stabilizing when energy reaches ≥80 mJ, recommending 80 mJ as the optimal energy level (balancing ignition reliability and energy consumption economy). Laser longitudinal depth significantly influences flame propagation characteristics, showing a 23% increase in flame propagation speed at 15 mm depth and a reduction of unburned methanol mass fraction to 0.8% at the end of combustion.