New Concepts for Measuring Flame Spread Properties

An experimental procedure is described which can be used to derive data relevant to the prediction of ignition and flame spread on materials. This procedure offers a direct method for determining material property data suitable for use in mathematical fire models. The apparatus utilizes a radiant heat source capable of supplying up to 6.5 W/cm² to a vertically oriented specimen. The test results pertain to piloted ignition of a vertical sample under constant and uniform irradiation and to lateral flame spread on a vertical surface due to an external applied radiant heat flux. The results can be used to display the maximum velocity and ignition time as a function of irradiance. Critical or minimum irradiances for spread and ignition are determined. An empirical correlation, based on heat conduction principles, is found to correlate the ignition data and also provides a more general interpretation for the flame spread results. Further analyses of the data yield effective values for the thermal inertia of the material (kρc), its ignition temperature, and a parameter related to flame temperature. These parameters appear to be phenomenological constants for each material, rather than factors dependent on the apparatus. Results are presented for a wide range of materials. Suggestions for extending the results to other flame spread conditions are presented.