Contaminant Entrainment in a Liquid Fuel Fire
Some fires may involve fuels that are contaminated with airborne particles such as hazardous chemicals or radioactive materials, and therefore pose a significant health risk by the potential inhalation of the contaminated material. In particular, consider a relatively inert solid material which is sub-micron in size that is suspended in a liquid solvent. Various mechanisms can lead to the solid becoming entrained in the air. First, as a liquid fuel is consumed it typically transitions through a boiling regime. As the vapor bubbles rupture at the liquid surface, the liquid response can result in the formation of film drops (collapsing bubble film) or jet drops (caused by liquid rapidly filling the vapor void). Surface wave action can also result in bubble formation and entrainment as the bubbles collapse. This mechanism is generally a function of wind speed and fluid properties. Also, mass may be entrained from a residual layer formed after consumption of the fuel. This paper reviews the existing literature on these entrainment mechanisms. Based on data from the review, the results from a Lagrangian/Eulerian coupled computational transport code are compared to some existing data on the entrainment of contaminants from liquid fuel fires. Since the multi-phase mechanistic prediction of the entrainment is not mature, the methods employ coupling of correlation data to the computational fluid dynamics (CFD) code.