Effect of the fuel boiling point on the boilover burning of liquid fuels spilled on water

Abstract

The burnign of a liquid fuel floating on water is a problem of particular interest in fires resulting from accidental liquid fuel spills in open waters. Under certain conditions, the fuel burns in a disruptive fashion, known as boilover, which is caused by the boiling of the water underneath, and results in a sharp increase in burning rate and external radiation, and often in the explosive burning of the fuel. In this work, smallscale experiments were conducted to determine the effect of the fuel boiling point on the onset and characteristics of the boilover burning of a fuel spilled on water. To simplify the nature of the results, the fuel layer thickness and pool diameter were kept constant. Fuels tested ad boiling points ranging from 383 to 560 K, and included a heating oil, a crude oil, and five single-component fuels. Measurements were conducted on the liquid fuel and water temperature histories, with emphasis on the temperature at the fuel/water interface. These measurements were complemented with the simultaneous video recording of the bubble nucleation and dynamics at the fuel/water interface, and of the flame plume above the pool. The results of the study corroborate that boilover is due to the nucleation of the water at the fuel/water interface, and that, consequently, for boilover to occur the boiling point of the fuel must be at least above the saturation temperature of water. The boilover intensity increases as the boiling point of the fuel increases, primarily because the thickness of the fuel and superheated water layers is larger at the onset of boilover. Thicker fuel and superheated water layers result in a stronger and faster ejection of the fuel from the pan toward the flame, and consequently in a more explosive and hazardous boilover event.