Author: Julien Gsell
Master of Science Thesis in Fire Protection Engineering, University of Ulster, Northern Ireland, 2010
Abstract
The introduction of water mist used as an extinguishing agent by fire fighters and operated from outside of the enclosed fire room is a revolution that started in the last decade. More than a complement to traditional fire fighting, the only hand held lance capable of such results is named the Cutting Extinguisher.
Its recent development raised the interest of rescue services and fire engineers, conducting researchers to the first studies of the nozzle characteristics. However, many points regarding the abilities of the Cutting Extinguisher remain unexplored as yet. Some experiments were conducted for water mist measurement, fire tackling time and structural member drilling effectiveness, but there are still a number of unexplored parts in the literature, especially about the behaviour of water mist within the involved volume, and the variations of its capabilities related to the type, geometry and ventilation factor of the fire.
This report has been written with the aim of answering a part of these remaining questions, as well as studying further on some induced effects of the introduction of water mist in an enclosure. It is based on the analysis of a series of full scale experiments, carried out in a compartment of 60 m3. Over a period of three weeks, 25 tests were conducted, in a situation without fire, and 8 real burnings were achieved, involving the variation of both fire and extinguishing scenarios on the basis of three main parameters which were: the change of fuel surface, opening area, and water flow rate. The cold trials concerned the recording of the amount of water distribution per unit time, regarding the position of the mouthpiece, and visible behaviour of the mist, thanks to visual and video observation. The fire measurements were conducted thanks to instrumentation of the studied compartment by a volumetric meshing of 99 thermocouples, combined with heat flux, pressure and video recording.
The data analysis presents the results of findings in terms of water mist calibration, spray pattern, shaping and volumetric displacement, as well as concerning the flame blowing ability, cooling effectiveness, dependence on the studied parameters and induced consequences of the extinguishment.
