Characterizing boilover behaviours in thin-layer diesel pool fires: The critical roles of lip height and water layer thickness

The ignition of multi-component fuels spilled on water can trigger complex boilover phenomena, leading to severe combustion events that pose significant risks to nearby structures and disrupt energy utilization in chemical and process industries. This study systematically investigates the coupled effects of lip height and water layer thickness on the combustion characteristics of thin-layer diesel pool fires, spanning diameters from 7 cm (conduction-dominated) to 20 cm (radiation-dominated). Experimental results demonstrate that the mass burning rate of thin-layer pool fires decreases progressively with increasing lip height during steady-state combustion. Based on burning characteristics, boilover phenomena are classified into three distinct regimes: single boilover, multiple boilover, and no boilover. Notably, the intensity of boilover in fires with a 3 cm water layer is nearly four times greater than in those with a 1 cm water layer, driven by elevated superheated water temperatures exceeding 130 °C. Through dimensionless analysis, a modified correlation is developed to characterize boilover intensity under varying lip heights and water layer thicknesses. Additionally, a comprehensive instability analysis at the oil/water interface is conducted to elucidate the underlying mechanisms governing different boilover behaviours. These findings offer new insights into the burning behaviour of thin-layer boilover fires, contributing to enhanced fire risk assessment and prevention strategies in the future.