Characteristics and mechanisms of methanol-supercritical water combustion: Optimization for auto-ignition and forced ignition

Supercritical hydrothermal combustion is an efficient and environmentally friendly advanced combustion technology that has gained significant attention in recent years. This study investigates the ignition characteristics and mechanisms of both auto-ignition in a methanol-supercritical water environment and forced ignition. The results indicate that the lowest auto-ignition temperature is reduced to 275 °C for a 20 wt% feed. For forced ignition, the lowest ignition temperature is further reduced to 25 °C for a 40 wt% methanol solution in contact with an 800 °C hot surface. In the methanol-supercritical water environment, the initial fuel experiences partial oxidation in oxygen-lean regions and vigorous oxidation in oxygen-rich regions. The initial temperature will ignite the initial fuel instead of heating the feed to its auto-ignition temperature. While the bulk fluid remains subcritical or near ambient temperature, the fluid adjacent to the hot surface is heated to a supercritical state. The supercritical water acts as both reaction medium and reactant, initiating hydrothermal combustion. Through development and split, the ignition core ignites all the feed and the flame root stabilizes on a circular plane with a fluid flow rate of approximately 0.23 m⋅s⁻¹ eventually.