Upward Fire Spread: Key Flammability Properties, Similarity Solutions And Flammability Indices

Abstract

Measurement methods and their interpretation are discussed for determining key flammability properties of charring and non-charring materials that are required as an input to a comprehensive Upward Flame Spread and Growth computer model. In addition, desirable similarity situations for upward flame spread are outlined which provide simple analytic solutions for upward flame spread rates. These solutions can be used to provide insight and illustrate how the material properties affect upward flame spread. Among other material parameters (critical heat flux, ignition parameter, xR, xA), an important parameter is the material flammability number, MFN = (xR+ xC). ?Hc /?Hv, (xR radiant fraction and xC convective fraction of the heat release rage applies back to the surface, ?HC, = heat of combustion, ?Hv = effective heat of gasification), which affects monotonically the ratio of flame height to pyrolysis length. For low values of this parameter (so that Zf/Zp < 1), self-sustained flame spread will even stop (except if the material is heated uniformly throughout up to the pyrolysis temperature by an external heat flux).