Influence of component fractions and structure characteristic on the combustion behavior of densified wood

Abstract

Densified wood (DW) is a promising structural material in high-rise timber buildings. However, fire safety issues restrict its applications. The key is to understand the influence of component fractions and dense structure on DW combustion. Here, the combustion behavior of DW is experimentally and numerically investigated. Thermogravimetric analysis (TGA) results showed that DW has 29 K earlier and 1.01 × 10 −4 s −1 lower peak mass loss rate, 5 % higher residue mass than natural wood (NW) due to the component weight fraction changes by delignification . ThermaKin was applied, combined with TGA, differential scanning calorimetry and microscale combustion calorimetry , to obtain pyrolysis kinetics and thermodynamics of wood. Cone calorimeter tests showed DW has delayed ignition time because its high density enhances heat conduction and decelerates wood surface temperature increase. DW has delayed but higher value of second heat release rate peak and lower heat of combustion due to its dense structure leading to a thermally insulating and condensed char layer. Radial thermal conductivity of wood linearly increases with density. Temperature poses greater impact on thermal conductivity than density. An optimized thermal conductivity equation is proposed and applied to predict the cone calorimeter tests, yielding good agreement. • DW has earlier/lower pyrolysis peak, higher residue mass due to delignification. • ThermaKin and STA/MCC are combined to get kinetics and thermodynamics of pyrolysis . • DW has delayed t ig and 2nd HRR peak , higher (lower) value of 2nd HRR peak, ( Δ H c , mean ). • Both T and ρ enhance wood thermal conductivity , T has higher impact. • Predictions with optimized thermal conductivity well match experiment results.