Pool Fire Behavior in a Small and Mechanically Ventilated Compartment
Several fire tests were conducted with heptane and in a chamber of 1 m3, in which the smoke exhaust was done by a fan. The aim was to analyze the rate of mass loss of fuel and the behavior of the flame in the case of under-ventilated fires. For all tests,
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Pool Fire Behavior in a Small and Mechanically Ventilated Compartment Alexis Coppalle, Alvin Loo, and Philippe Aine´
Abstract
Several fire tests were conducted with heptane and in a chamber of 1 m3, in which the smoke exhaust was done by a fan. The aim was to analyze the rate of mass loss of fuel and the behavior of the flame in the case of under-ventilated fires. For all tests, the oxygen concentration in the flow which feeds the base of the flame decreases continuously. However the mass loss rate increases or decreases depending on the ventilation in the compartment. This can be explained by the respective contribution of the flame and of the smoke layer in the heat transfer toward the liquid fuel. If the ventilation of the room is sufficient, a periodic phenomenon of propagation/expansion of the flame is also observed, with a characteristic frequency that has been determined by an analysis of the flame images and which is close to 1 Hz. Keywords
Pool fire under-ventilated flame Smoke Radiation
Nomenclature
Greek Symbols
D Fs-F
αF eF
L MLR MLRfree T Yo Yo,/
Pool fire diameter View factor between the fuel surface and the smoke layer Heat of gasification (kJ/g) Mass loss rate (g/m2/s) Mass loss rate with free-burning conditions Temperature Oxygen concentration (%volume) Oxygen concentration in ambient air (%volume)
Subscripts F s
9.1
A. Coppalle (*) National Institute of Applied Sciences, UMR 6614 CORIA, rue de l’Universite, St Etienne du Rouvray 76801, France e-mail: [email protected] A. Loo P. Aine´ AREVA, Paris, France
Absorptivity of the liquid fuel Emissivity of the liquid fuel
Fuel Smoke
Introduction
The compartmented and under-ventilated fires are now an important topic, as they can occur in habitat or in industry. They may be encountered when the ventilation of compartments is strongly controlled, as in the new buildings or in the confined spaces of some industries, in particular in the nuclear industry. These conditions can lead to scenarios during which the fire consumes quickly the air available in the compartment. The combustion is then made with a lack of air and
# Springer Science+Business Media Singapore 2017 K. Harada et al. (eds.), Fire Science and Technology 2015, DOI 10.1007/978-981-10-0376-9_9
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the flame extinction may also occur. In these cases, it can be emitted a significant quantity of combustible vapors, mainly after extinction because of the thermal inertia of heated combustibles and also due to the convective and radiative fluxes that remain high on the surfaces of materials. The excess of combustible vapors may trigger a deflagration if a fresh air is introduced suddenly into the room. This thermal accident represents a serious hazard that people in the vicinity might be exposed as well as the emergency services. It is important to identify the key phenomena that control such scenarios, in order to determine the mass loss rate of combustibles and the flame behavior inside the compartment. The conditions that lead to the extinction of
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