Abstract Timber is becoming a popular construction material even for high-rise buildings despite its poorly understood fire behaviour. In a fire, timber—a natural polymer—degrades in the thermochemical process of charring, causing it to lose structural strength. In spite of significant research on the physics of charring, the chemical kinetics—reactions and kinetic parameters for pyrolysis and oxidation—remains a scientific challenge to model accurately. Current kinetic models are either computationally too expensive or neglect key chemical pathways. Here we derive a new appropriate kinetic model for fire science at the microscale using a novel methodology. First, we built a kinetic model for each component of timber (cellulose, hemicellulose, and lignin) from literature studies and experiments of the components. Then, we combined these three models into one kinetic model (8 reactions, 8 chemical species) for timber. This approach accounts for chemical differences among timber species. However, the timber model is only able to reproduce the trend in the experiments when literature parameters are used. Using multi-objective inverse modelling, we extract a new set of optimised kinetic parameters from 16 high-quality experiments from the literature. The novel optimised kinetic model is able to reproduce these 16 and a further 64 (blind predictions) experiments nearly within the experimental uncertainty, spanning different heating rates (1–60 K/min), oxygen concentrations (0–60 %), and even isothermal experiments (220–300 °C). Furthermore, the model outperforms current kinetic models for fire science in accuracy across a wide range of conditions without an increase in complexity. Incorporated into a model of heat and mass transfer, this new and optmised kinetic model could improve the understanding of timber burning and has the potenial to lead to safer designs of timber buildings.

中文翻译：

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微尺度木材炭化的非均相动力学

摘要 尽管人们对木材的火灾行为知之甚少，但木材正成为一种流行的建筑材料，即使是高层建筑。在火灾中，木材——一种天然聚合物——在炭化的热化学过程中降解，导致其失去结构强度。尽管对炭化物理学进行了大量研究，但化学动力学——热解和氧化的反应和动力学参数——仍然是准确建模的科学挑战。当前的动力学模型要么计算成本太高，要么忽略了关键的化学途径。在这里，我们使用一种新颖的方法在微观尺度上为火灾科学推导出了一个新的合适的动力学模型。首先，我们通过文献研究和成分实验为木材的每个成分（纤维素、半纤维素和木质素）建立了动力学模型。然后，我们将这三个模型组合成一个木材动力学模型（8 个反应，8 个化学物质）。这种方法解释了木材物种之间的化学差异。然而，木材模型只能在使用文献参数时重现实验中的趋势。使用多目标逆向建模，我们从文献中的 16 个高质量实验中提取了一组新的优化动力学参数。新的优化动力学模型能够重现这 16 次和另外 64 次（盲预测）实验，几乎在实验不确定性范围内，跨越不同的加热速率（1-60 K/min）、氧气浓度（0-60 %），甚至等温实验 (220–300 °C)。此外，在不增加复杂性的情况下，该模型在各种条件下的准确性都优于当前的火灾科学动力学模型。结合到传热和传质模型中，这种新的优化动力学模型可以提高对木材燃烧的理解，并有可能导致更安全的木结构建筑设计。