Document Type dissertation Author Name Beaulieu, Patricia Email Address patricia.beaulieu at fmglobal.com URN etd-121905-082146 Title Flammability Characteristics at Heat Fluxes up to 200 kW/m2 and The Effect of Oxygen on Flame Heat Flux Degree PhD Department Fire Protection Engineering Advisors Nicholas A Dembsey, Advisor Robert G. Bill Jr., Co-Advisor John Woycheese, Co-Advisor Keywords ignition oxygen mass loss rate heat flux scalability burning flammability fire Date of Presentation/Defense 2005-11-02 Availability unrestricted
This dissertation documents two interrelated studies that were conducted to more fundamentally understand the scalability of flame heat flux.
The first study used an applied heat flux in the bench scale horizontal orientation which simulates a large scale flame heat flux. The second study used enhanced ambient oxygen to actually increase the bench scale flame heat flux itself. Understanding the scalability of flame heat flux more fully will allow better ignition and combustion models to be developed as well as improved test methods.
The key aspect of the first study was the use of real scale applied heat flux up to 200 kW/m2. An unexpected non-linear trend is observed in the typical plotting methods currently used in fire protection engineering for ignition and mass loss flux data for several materials tested. This non-linearity is a true material response. This study shows that viewing ignition as an inert material process is inaccurate at predicting the surface temperature at higher heat fluxes and suggests that decomposition kinetics at the surface and possibly even in-depth may need to be included in an analysis of the process of ignition. This study also shows that viewing burning strictly as a surface process where the decomposition kinetics is lumped into the heat of gasification may be inaccurate and the energy balance is too simplified to represent the physics occurring.
The key aspect of the second study was direct experimental measurements of flame heat flux back to the burning surface for 20.9 to 40 % ambient oxygen concentrations. The total flame heat flux in enhanced ambient oxygen does not simulate large scale flame heat flux in the horizontal orientation. The vertical orientation shows that enhanced ambient oxygen increases the flame heat flux more significantly and also increases the measured flame spread velocity.
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