Abstract This study comprises an assessment of the behaviour of wheat starch/pyrolysis gases hybrid mixtures under different operating conditions of Ignition Delay Time (tv) and nozzle geometry in the context of the 20-L Sphere Test. The behaviour of the system was determined through the study of the interaction between the chemical reactions of the phases and the turbulence levels produced by the different operating configurations. For these purposes, CFD simulations based on a coupled Eulerian-Lagrangian formulation were developed considering the two main steps of the test: i) Dispersion of the powder, and ii) Pyrolysis/gas-oxidation reactions. The CFD model included a few important improvements to other computational methodologies proposed in previous studies, such as the incorporation of more rigorous kinetic mechanisms for the devolatilization reactions of the starch particles and the combustion reactions of the pyrolysis gases. In parallel, experimental tests were performed in order to validate the CFD model and characterize the powder samples. In particular, the composition of the pyrolysis gases emitted by the particles was determined by a modified setup of the Godbert-Greenwald furnace, and the Particle Size Distribution (PSD) was measured through laser diffraction techniques. The performance of the CFD model was satisfactory in terms of predicting parameters related to the hydrodynamic or reaction-kinetic behaviour of the system, such as the pressure evolution during dispersion and the (dP/dt)m (average deviations from experimental values of ~4.0% and 11.9%, respectively). Furthermore, the results suggest that the combined effect of the dust-phase and gas-phase reactions have a distinctive dissipative effect on the turbulence levels and that higher turbulence decay levels during the explosion step of the test are related to higher explosion severities.

中文翻译：

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CFD-DPM 和小麦淀粉粉/热解气体混合混合物在 20-L 球体动力学的实验研究

摘要 本研究包括在 20 升球体测试的背景下，评估小麦淀粉/热解气体混合混合物在点火延迟时间 (tv) 和喷嘴几何形状的不同操作条件下的行为。系统的行为是通过研究各相的化学反应与不同操作配置产生的湍流水平之间的相互作用来确定的。出于这些目的，考虑到测试的两个主要步骤，开发了基于耦合欧拉-拉格朗日公式的 CFD 模拟：i) 粉末的分散，以及 ii) 热解/气体氧化反应。CFD 模型包括对先前研究中提出的其他计算方法的一些重要改进，例如为淀粉颗粒的脱挥发分反应和热解气体的燃烧反应引入更严格的动力学机制。同时，进行了实验测试以验证 CFD 模型并表征粉末样品。特别是，颗粒释放的热解气体的组成是通过戈德伯特-格林沃尔德炉的改进设置确定的，并且粒度分布 (PSD) 是通过激光衍射技术测量的。CFD 模型在预测与系统流体动力学或反应动力学行为相关的参数方面的性能令人满意，例如分散过程中的压力演变和 (dP/dt)m（与实验值的平均偏差约为 4.0 % 和 11.9%）。此外，