vertical wall and flame spread upward. A large amount of experimental data and theoretical models are currently available that correlate flame-spread characteristics with materials flammability properties (Hasemi, 1986; Saito et al., 1989; Cleary and Quintiere, 1991). The calculated results show a reasonable agreement with the experimental data (Cleary and Quintiere, 1991). However, the effects of melting or dripping on upward flame spread might be important if thermoplastics are used.
Another important flame-spread configuration for an airplane is flame spread under the ceiling. The limited studies that are available (Agrawal and Atreya, 1992; Atreya and Mekki, 1992) show that unusual flame instability might occur in this configuration. It is extremely difficult to predict the upward flame-spread process if only the chemical structure of the material and its dimensions are provided. Even more-detailed flame-spread models can be developed, including detailed chemical reactions, but their predictive capability would be still semi-quantitative.
Flame-spread and burning characteristics of upholstered furniture have been extensively studied. A theoretical model of fire growth on an upholstered chair, based on detailed radiative shape-factor calculation between the burning area and unburned region with empirical correlation for flame spread, has been reported (Dietenberger, 1992). However, the validity of the model and its accuracy have not yet been well established. These data and models might be of use for aircraft seats to describe how these seats bum in the event of a fire accident.
It is important to be able to predict the occurrence of flashover based on calculated local heat release rates. Given the heat feedback rate from a flame to the material surface, the generation rate of combustible degradation products is determined from the processes of heat-and mass-transport rates processes and also from degradation chemical reaction kinetics. Given the rate of supply of the combustible degradation products and their chemical composition, characteristics of the flame such as flame height and heat release rate are determined. Thus, the direct coupling between the energy feedback rate and the rate of supply of the combustible degradation products determines local heat release rate per unit surface area. Experimental results show that a flame tends to become more optically opaque with increases in flame size, and radiative feedback dominates over convective feedback; also radiative feedback is enhanced for a flame generated by the degradation products having higher aromatic content. At present, it is extremely difficult to calculate radiative transfer in a turbulent flame. There are still uncertainties in how to accurately model turbulence, formation and destruction of soot particulates (the radiation source), and how to calculate radiative heat transfer efficiently.
Since fire in an aircraft cabin is affected by interaction with its surroundings, such as air entrainment through openings or by the interaction of hot ceiling and walls with burning items, compartment fire models described in Chapter 3 and Appendix C are an important element in understanding an aircraft fire.