An advanced CFD (computational fluid dynamics) model has been developed to describe the combustion of wood pellets. It is based on a packed-bed approach and provides a realistic description of the combustion of pellets, resolved in 3D over the whole fuel bed. It considers the properties of the packed bed rather than the properties of the single fuel particles. Compared to a particle-based description, simulation times are shorter due to the reduced complexity. In the model, the local conditions in different parts of the fuel bed (temperatures, flow conditions, oxygen concentrations …) influence the various stages of the combustion process (drying, pyrolysis, charcoal gasification and combustion). The compaction of the fuel bed due to shrinkage of the fuel particles during conversion and the loss of the particle structure shortly before the conversion is complete are also included in the description. The formulation of the bed compaction, the radiation absorption model and the charcoal conversion reactions have been specifically tuned to the combustion of wood pellets. The detailed pyrolysis model includes not only the main components, but also higher hydrocarbon species and tars in a manner specific to the fuel considered. It has been combined with a chemical gas phase mechanism which is a reduction of a detailed mechanism developed for thermo-chemical biomass conversion. The model has been validated against measurement data from a lab-scale batch reactor, and then applied to simulate the fuel bed of a commercial pellet stove. The simulation results are in good agreement with the corresponding measurements.

中文翻译：

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用于颗粒燃烧的新型填充床 CFD 模型：验证及其在炉子中的应用


我们开发了先进的 CFD（计算流体动力学）模型来描述木屑颗粒的燃烧。它基于填充床方法，提供对颗粒燃烧的真实描述，并以 3D 形式解析整个燃料床。它考虑填充床的特性而不是单个燃料颗粒的特性。与基于粒子的描述相比，由于复杂性降低，模拟时间更短。在模型中，燃料床不同部分的局部条件（温度、流动条件、氧气浓度……）影响燃烧过程的各个阶段（干燥、热解、木炭气化和燃烧）。描述中还包括由于转化期间燃料颗粒的收缩而导致的燃料床的压实以及在转化完成之前不久颗粒结构的损失。床压实、辐射吸收模型和木炭转化反应的公式专门针对木颗粒的燃烧进行了调整。详细的热解模型不仅包括主要成分，还以所考虑的燃料特定的方式包括高级碳氢化合物和焦油。它与化学气相机制相结合，该机制是为热化学生物质转化而开发的详细机制的简化。该模型已根据实验室规模间歇式反应器的测量数据进行了验证，然后应用于模拟商用颗粒炉的燃料床。仿真结果与相应的测量结果非常吻合。