Experimental study on offshore fires in cross air flow above water induced by the underwater release of natural gas

The flame and gas spread caused by underwater leak will poses a significant threat to the safety of offshore facilities and personnel. To explore the behavior of offshore fires induced by released natural (methane) gas from submarine pipelines, more than 300 tests were conducted. The variations of underwater plume width with the leakage flow rate, depth of leakage point was quantified and analyzed, then the evolution of flame geometry with cross air flow above water induced by the underwater release of natural gas was revealed. It was found that, a dimensionless parameter beta was used to represent the effect of bubble buoyancy and a correlation for underwater plume was proposed to describe the bubble width on the water surface with various leakage orifice depths. The flame duration above water surface due to reduced buoyancy was discussed and it found that the stable underwater plume can lead a longer flame duration (beta>3.3). For the flame geometric of offshore fire plume above water under cross air flow, the vertical flame length decreases with increase of cross air flow, while the horizontal flame length increases with the cross-air flow for a given gas flow rate. Finally, a correlation of flame geometry for offshore fire with the effect of cross air flow was proposed, based on the competition between the flame buoyancy and inertia force caused by cross air flow.