Simultaneous in-situ measurements of gas temperature and pyrolysis of biomass smoldering via X-ray computed tomography
Simultaneous in-situ measurements of gas temperature and pyrolysis of biomass smoldering via X-ray computed tomography
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DOI：
10.1016/j.proci.2020.06.070
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发表时间：
2021-04-10
影响因子：
3.4
通讯作者：
Ihme, Matthias
中科院分区：
文献类型：
--
作者：
Boigne, Emeric;Bennett, N. Robert;Ihme, Matthias
采用原位x射线计算机断层扫描（XCT）技术研究了亚毫米尺度下生物质的阴燃动力学。该技术提供了气体温度和生物质密度的同步和空间分辨信息，从而能够跟踪热解和炭氧化前沿。为了实现良好的加热和流动调节，橡木生物质样品在管道内的扩散火焰上方进行测量，每体积的总氧浓度分别为6%和11%。实验在实验室XCT系统上进行。流动用Kr稀释以增加气相中的x射线衰减，从而允许同时进行样品密度和周围温度的3D测量。XCT扫描每90秒进行一次，空间分辨率为135 μ m，高空间分辨率使与热解和炭氧化相关的阴燃过程的体积可视化成为可能。这些测量结果表明，颗粒结构如何影响火焰稳定并诱发热解前沿的指状，而裂纹的形成则加速了局部炭氧化。通过XCT对样品质量的评估与称重传感器的测量结果进行了比较，显示出良好的一致性。建立了一个低阶模型，根据x射线数据评估热解和氧化锋随时间的传播速度，并与表面隐窝速度进行了比较。(c) 2020燃烧研究所。Elsevier Inc.出版。版权所有。
In-situ X-ray computed tomography (XCT) imaging is employed to investigate the smoldering dynamics of biomass at the sub-millimeter scale. This technique provides simultaneous and spatially-resolved information about the gas temperature and the biomass density, thereby enabling tracking of the pyrolysis and char oxidation fronts. To achieve well-controlled heating and flow conditioning, oak biomass samples are instrumented above a diffusion flame inside a tube, with total oxygen concentrations of 6% and 11% per volume. Experiments are performed on a laboratory XCT system. The flow is diluted with Kr to increase X-ray attenuation in the gas phase thus allowing for simultaneous 3D measurements of sample density and surrounding temperature. XCT scans are acquired every 90 s at a spatial resolution of 135 mu m. The high spatial resolution enables the volumetric visualization of the smoldering process that is associated with pyrolysis and char oxidation. These measurements show how the grain structure affects flame stabilization and induces fingering of the pyrolysis front, while crack formation accelerates the char oxidation locally. Evaluations of the sample mass via XCT are compared with load cell measurements, showing good agreement. A low-order model is developed to evaluate the propagation speeds of pyrolysis and oxidation fronts from the X-ray data over time, and comparisons are made with the surface recess speed.(c) 2020 The Combustion Institute. Published by Elsevier Inc. All rights reserved.