Effect of oxygen on the burning rate of wood
Section snippets
Introduction to wood fires
Engineered wood is becoming a popular construction material due to its strength, lightweight, and sustainability [1]. It is made by gluing wood fibres (Medium Density Particleboard), chips (Low-Density Particleboard), or planks (Cross Laminated Timber) together in various assemblies. However, a limited understanding of the fire behaviour of engineered wood hinders its uptake [1]. Specifically for tall buildings, wooden products are largely prohibited or too costly due to the strict fire safety
Experimental method
The experiments were conducted using a Fire Propagation Apparatus (FPA) following the ASTM E 2058 standard. In an FPA, the fuel sample is exposed to a radiative heat flux, and a pilot ignition source placed above its free surface. In this study, the range of radiative heat imposed varied from 10 to 70 kW/m2 and was maintained constant for the whole duration of the experiment. The sample mass was continuously measured and the exhaust gases were analysed for composition, temperature, and flow
Model validation and analysis
The model was developed at the microscale and mesoscale against several experiments based on our previous work on natural wood [23,29]. Engineered wood differs from natural wood due to the presence of resin (affects kinetic model and heat of reactions), absence of grain direction (thermal conductivity), density gradient (density), and porosity gradient (porosity, pore diameter). We found the resin to have an insignificant influence on the chemical kinetics as our chosen kinetic model performs
Conclusions
In this paper, we experimentally and computationally characterised the influence of oxygen concentration and other variables on the burning behaviour of particleboard. Heat flux had a significant influence, while density and sample thickness had no effect on the charring rate and time-to-flaming ignition. Oxygen concentration controls the mode of burning with pyrolysis dominating below 4% [O2]a, smouldering between 4 and 15% [O2]a, and flaming above 15%. These thresholds agree with the
Declaration of Competing Interest
None.
Acknowledgment
The authors thank EPSRC, Arup, and BRE Trust for financial support and the University of Edinburgh for the experimental facilities used. Furthermore, we thank members of Imperial Hazelab for insightful discussions and helpful comments.
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