Effect of structural characteristics on charring shrinkage and cracking of densified wood under radiative heatings

IF 3.4 3区 工程技术 Q2 ENGINEERING, CIVIL Fire Safety Journal Pub Date : 2024-06-11 DOI:10.1016/j.firesaf.2024.104204
Tianyang Chu , Chuangang Fan , Chunli Liu , Saiya Feng , Zhengyang Wang , K.M. Liew
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Abstract

Densified wood (DW) is a novel engineering material with excellent mechanical properties. It forms a thermally insulating and hardly-cracked char layer during pyrolysis and combustion. However, the scientific fundamentals regarding how wood structural characteristics (e.g. density) affect its charring behavior remain unknown, which is important for the fire safety of wood. In this work, the charring shrinkage and cracking of NW and DW with various densities (ρ) under heating exposures (Qr) are investigated and analyzed. Partial crack closure was observed due to the oxidation. As wood ρ increases or Qr decreases, the number of cracks (Nc) decreases and cracking time (tc) is delayed because both the surface temperature (Tsurf) and altered thermal stress concentrations on the wood surface are reduced. DW presents an earlier mass loss peak and lower peak value due to the delignification. DW presents high fluctuations in Tsurf due to the combing effect of thermal inertia and radial rebound. As wood ρ increases, char shrinkage depth at tc decreases and shrinkage gradient at tc increases first and then decreases. An empirical correlation is proposed and well-predicts the Nc based on ρ and Qr. It can be potentially implemented in the combustion model to improve prediction accuracy.

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结构特征对辐射加热条件下致密木材炭化收缩和开裂的影响
致密木材(DW)是一种新型工程材料,具有优异的机械性能。它在热解和燃烧过程中会形成隔热且几乎不开裂的炭化层。然而,有关木材结构特征(如密度)如何影响其炭化行为的科学基础仍然未知,而这对木材的防火安全非常重要。在这项工作中,研究和分析了不同密度 (ρ) 的 NW 和 DW 在加热暴露 (Qr) 下的炭化收缩和开裂情况。由于氧化作用,观察到部分裂缝闭合。随着木材 ρ 的增大或 Qr 的减小,裂纹数量(Nc)减少,开裂时间(tc)推迟,因为木材表面温度(Tsurf)和改变的热应力浓度都降低了。由于木质素的脱落,DW 的质量损失峰值较早,峰值较低。由于热惯性和径向反弹的组合效应,DW 的 Tsurf 波动较大。随着木材 ρ 的增大,tc 处的炭收缩深度减小,tc 处的收缩梯度先增大后减小。根据 ρ 和 Qr 提出了一种经验相关性,并能很好地预测 Nc。可以将其应用于燃烧模型,以提高预测精度。
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来源期刊
Fire Safety Journal
Fire Safety Journal 工程技术-材料科学:综合
CiteScore
5.70
自引率
9.70%
发文量
153
审稿时长
60 days
期刊介绍: Fire Safety Journal is the leading publication dealing with all aspects of fire safety engineering. Its scope is purposefully wide, as it is deemed important to encourage papers from all sources within this multidisciplinary subject, thus providing a forum for its further development as a distinct engineering discipline. This is an essential step towards gaining a status equal to that enjoyed by the other engineering disciplines.
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