Modeling of Ceiling Fire Spread and Thermal Radiation.
Abstract
The pressure modeling technique is used to study fire spread under five different ceiling materials and analytical and numerical techniques are used to compute thermal radiation to floor level from the resultant layer of hot gases near the ceiling. In the physical modeling part of the study, measurements are obtained at one atmosphere (full-scale) and at elevated air pressure characterizing fire growth in a ceiling channel exposed to a developing PMMA wall fire. Pressure modeling predictions of flame spread rates under a PMMA ceiling and flame lengths under an inert ceiling are found to be in reasonable agreement with full-scale behavior. Although fire spread under aircraft material ceilings occurs only at elevated pressure and not at one atmosphere (due to charring effects and the use of full-scale material thickness in the models), exponential growth factors characterizing fire spread rates, mass loss rates and radiant heat loss in the model tests are used to group the five ceiling materials according to fire growth hazard. In the second phase of the study, an exact, numerical solution technique is formulated for computing the radiant flux from hot gas layers with arbitrary, three-dimensional variations in gas temperature and absorption coefficient. A simplified analytic approximation involving the use of a suitably averaged gas temperature and absorption coefficient is compared with the exact technique for the calculation of radiant flux to targets below the ceiling gas layer. It is found that the analytic approximation is adequate even when the gradients in temperature are much larger than those expected from real aircraft cabin fires. (Author)
Document Details
- Document Type
- Technical Report
- Publication Date
- Oct 01, 1981
- Accession Number
- ADA107590
Entities
People
- A. T. Modak
- M. K. Mathews
- R. L. Alpert