Controlling mechanisms of burning rate enhancement while using Flame Refluxer technology during in situ burning of crude oil spills

Abstract

ABSTRACTThe focus of this study is to quantify the controlling mechanisms, which increases the burning rate of a pool fire using a Flame RefluxerTM. Part of the Flame RefluxerTM, is exposed to the fire and is heated up transferring heat to the fuel pool layer to which it extends. This enhances the conventional heat transfer that occurs only through the pool surface by transferring the heat from a fire to an in-depth layer of the liquid. Both sensible heat and heat of vaporization are supplied at increased rates by the submerged material. As an additional important effect, nucleate boiling onsets at the surface of the inserted material that generates bubbles of fuel vapor. These bubbles are transported to the surface of the pool, where they burst and release the v0061por to the gas-phase. While doing so, additional processes such as formation of micron-sized droplets or small jets of liquid fuel from the break point occur. This phenomenon causes additional fuel in liquid phase transported to the gas-phase, where they vaporize, ignite and burn in heterogeneous mode. Therefore, the processes involved in FR occur in three steps; enhancement of heat transfer to the liquid causing nucleate boiling, formation of bubbles and their transport, and dynamics of bubble breakage at the pool surface causing transfer of liquid fuel in the form of tiny droplets or jets towards the gas-phase. This study analyzes the influence of bubbles on the burning behavior of a pool fire using a simple experiment involving burning ethanol as a fuel. Ethanol is used due to its transparency and hence bubble behavior is easily observable on the heater surface. A 5cm x 5cm glass enclosure constantly replenished with ethanol serves as the burning pool. A solid aluminum block (8.8 cm tall x 3.6 cm wide x 1.2 cm thick) is placed in the flame to act as the Flame RefluxerTM. Bubble counts and burning rate measurements indicate the influence of the bubbles on the overall burning rate of the liquid pool.