AI 中文总结
本研究采用LES和拉格朗日点颗粒模拟JHC燃烧器，对比两种氧化模型和辐射模型，发现点火位置、温度阈值与颗粒尺寸对点火的影响，结果与实验存在差异。
AI 中文摘要
微米级铁粉是一种快速发展的新型储能技术。为改进实际铁粉燃烧器的设计，需充分理解此类场景下的点火行为。本研究采用大涡模拟（LES）和拉格朗日点颗粒，对Hameete等人（2024）设计的用于实验室规模湍流火焰中铁颗粒点火测试的热伴流射流（JHC）燃烧器进行数值模拟。模拟该JHC燃烧器的两种模式：开放火焰和封闭火焰，与实验参考一致。采用两种铁氧化速率模型——一阶模型和氧化层模型，以研究其对捕捉点火行为的影响。对于两相之间的辐射传热，考虑了简化的斯特藩-玻尔兹曼近似模型和P1模型，与Ramaekers等人（2025）的研究类似。火焰结构分析表明，点火发生在射流的圆周处，伴流的破裂有助于点火。在更高的伴流温度（$T_\text{coflow}$）下，点火起始和氧化完成时间更早，发生在射流破裂之前。使用氧化层模型时，颗粒点火所需的最低伴流温度为1125K，完全氧化温度为1250K；使用一阶模型时，对应温度分别为800K和900K，这两种结果均与Hameete的实验结果不匹配。可预测的是，封闭火焰的氧化程度更高。对于所选的颗粒分布，P1模型表现出更高的辐射热损失，导致氧化程度略低。对部分氧化的颗粒集合的分析表明，在喷嘴上方足够高度处的整体氧化程度反映了颗粒点火概率。关于颗粒尺寸的进一步分析显示，较大颗粒的点火失败更为普遍。
英文摘要
Micron-sized iron powders are a rapidly advancing novel energy storage technology. In order to improve the design of real-world iron-powder combustors, adequate understanding of the ignition behavior in such settings is necessary. In this work, a jet-in-hot-coflow (JHC) burner designed by Hameete et al. (2024) to test ignition of iron particles in lab-scale turbulent flames is modeled numerically using LES and Lagrangian point-particles. The JHC burner is simulated in two different modes--an open flame and an enclosed flame--similar to the experimental reference. Two iron-oxidation-rate models--the first-order model and oxide-layer model--are used to examine the effect on capturing the ignition behavior. For the radiative heat transfer between the two phases, a simplified Stefan-Boltzmann approximation model and the P1 model are considered, similar to Ramaekers et al. (2025). Analysis of flame structure indicates ignition in the circumference of the jet, aided by the break-up of the coflow. At higher $T_\mathrm{coflow}$, ignition onset and oxidation completion is earlier prior to jet break-up. Minimum coflow temperature for particle ignition with the oxide layer model is $1125\mathrm{K}$ with complete oxidation at $1250\mathrm{K}$, and for the first-order model at $800\mathrm{K}$ and $900\mathrm{K}$, respectively. Both of these results do not match the experimental results of Hameete. Oxidation degree is predictably higher for enclosed flames. For the chosen particle distribution, the P1 model exhibits higher radiative heat loss and results in a slightly lower oxidation degree. Analysis on particle ensembles with partial oxidation shows that the overall oxidation degree at a sufficient height above the nozzle reflects particle ignition probability. Further analysis in regards to particle size shows ignition failure is more prevalent in larger particles.
CommentsPreprint accepted for publication in Proceedings of the Combustion Institute. Supplementary material available upon request or at final publication
