Global Equivalence Ratio Concept and the Formation Mechanisms of Carbon Monoxide in Enclosure Fires.
Global Equivalence Ratio Concept and the Formation
Mechanisms of Carbon Monoxide in Enclosure Fires.
Pitts, W. M.
Progress in Energy and Combustion Science, Vol. 21,
carbon monoxide; enclosures; building fires; compartment
fires; fire gases; global equivalence ratio; kinetic
models; pyrolysis; reduced scale enclosures;
This report summarizes a large number of investigations
designed to characterize the formation of carbon
monoxide (CO) in enclosures fires - the most important
factor in fire deaths. It includes a review analysis of
the studies which form the basis for the global
equivalence ratio (GER) concept. Past and very recent
(some as yet unpublished) investigations of CO formation
in enclosure fires are reviewed. Based on the findings,
two completely new mechanisms for the formation of CO,
in addition to the quenching of a fire plume by a rich
upper layer, which is described by the GER concept, are
identified. The first is the result of reaction between
rich flame gases and air which is entrained directly
into the upper layer of an enclosure fire. Detailed
chemical-kinetic modeling studies have demonstrated that
CO will be generated by these reactions. The second is
due to the direct generation of CO during the pyrolysis
of oxygenated polymers (such as wood) which are located
in highly vitiated, high-temperature upper layers. The
findings of these studies form the basis of an analysis
that provides the guidelines for when the use of the GER
concept is appropriate for predicting CO formation in
enclosure fires. It is concluded that there are limited
conditions for which such use is justified.
Unfortunately, these conditions do not include the types
of fires which are responsible for the majority of fire
deaths in building fires.