Journal of Fire Sciences current issue

Enclosure Fires, Gravity Waves, and the Backdraft Problem

Eliasson, J., Guigay, G., Karlsson, B. — 2008-09-11

The air flow to an underventilated compartment fire often depends on the flow velocities in the gravity wave of cold air that feeds the fire with oxygen. This problem has been studied in laboratory experiments and by CFD simulations. The main problem seems to be whether mixing and entrainment between the two layers of hot and cold air has a profound effect on the flow velocities. In this article, an analytical gravity wave model that can calculate the velocities in a simple gravity wave is presented. This model uses the equations of stratified flow hydraulics and the translatory wave solution of the flow equations. It is found that the velocities of the model compare very well to the velocities reported from laboratory tests and numerical simulations. Numerical simulations of stratified flow in a CFD model are discussed with respect to model construction. It is concluded that the densimetric Froude number is the main parameter for the velocity calculations and the length/height ratio is important for the friction forces.

Synergistic Effect of Lanthanum Oxide on Intumescent Flame-Retardant Polypropylene-based Formulations

Jing Wu, , Yuan Hu, , Lei Song, , Wenjie Kang, — 2008-09-11

Synergistic effects of lanthanum oxide (La₂O₃) on the flammability and thermal properties of intumescent flame-retardant polypropylene (IFR-PP) composites are investigated in the study. The limiting oxygen index (LOI), UL-94 test, and cone calorimeter results show that the flame retardancy of IFR-PP is improved significantly by the introduction of La₂O₃. The results of thermogravimetric analysis (TGA) indicate that thermal stability of IFR-PP is also enhanced. SEM pictures reveal that La₂O₃ addition improve the formation of a homogenous and compact intumescent char layer on the surface of the composites. The possible mechanism of the synergistic effects between La₂O₃ and IFR is proposed in the paper.

A Comparative Study of Effectiveness of Smoke Alarms in Two Types of Buildings

Yaping He, , Nelson, D. — 2008-09-11

Fire or smoke alarms are crucial components in building fire safety systems. The effectiveness of fire alarms is investigated in this article. A relationship between effectiveness, efficacy, and reliability is formulated. A comparative study of the effectiveness of fire alarms in two types of occupancies is conducted using the published laboratory and field study results. The current study revealed the difference between the effectiveness of the fire alarm systems in dwelling and commercial stores.

An Experimental Study of Upward Flame Spread and Interactions Over Multiple Solid Fuels

Shih, H.-Y., Wu, H.-C. — 2008-09-11

Upward flame spread and flame interactions over multiple solid fuels are experimentally studied, and the effects of flame interactions on the flame spreading rates are analyzed. Flame spreading characteristics and spreading rates are measured and compared for six different geometric arrangements of thin solids at different solid width and separation distance between solids. The flame spread rate increases as the separation distance between the parallel solids decreases because of the flow channeling effect and radiation interactions, which reaches the maximum at an intermediate separation distance and then decreases as the separation distance becomes smaller due to the flow resistance and limited thermal expansion. To compare the six types of solid geometry studied, the highest flame spread rate is enclosure type of solids, followed by -shaped solids, four parallel solids, two parallel solids, L-shaped solids, and single solid.

Combustion Behavior of Intumescent Flame Retardant Polypropylene Composites

Chuanmei Jiao, , Jun Zhang, , Feng Zhang, — 2008-09-11

The combustion behavior of polypropylene (PP) composites containing intumescent flame retardant additives, i.e., melamine pyrophosphate (MPP) and 1-oxo-4-hydroxymethyl-2,6,7-trioxa-1-phosphabicyclo[2.2.2]octane (PEPA) was characterized by limiting oxygen index (LOI), UL 94 and the cone calorimeter. It has been found that the PP composite containing only PEPA does not show good flame retardancy even at 30% additive level. Compared with the PP/PEPA binary composite, the LOI values of the PP/PEPA/MPP ternary composites at the same additive loading are all increased, and UL 94 rating of the ternary composite (PP3) studied is raised to V-0 from no rating (PP/PEPA). The cone calorimeter results show that the heat release rate and mass loss rate of some ternary composites decrease in comparison with the binary composite.