DEM/CFD modeling of the fuel conversion in a pellet stove
DEM/CFD modeling of the fuel conversion in a pellet stove
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DOI：
10.1016/j.fuproc.2016.06.005
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发表时间：
2016-11
影响因子：
7.5
通讯作者：
J. Wiese;F. Wissing;D. Hoehner;S. Wirtz;V. Scherer;Ursula Ley;Hans Martin Behr
中科院分区：
文献类型：
--
作者：
J. Wiese;F. Wissing;D. Hoehner;S. Wirtz;V. Scherer;Ursula Ley;Hans Martin Behr
本研究提出了一种模拟家庭供暖系统中木屑颗粒燃烧的方法。到目前为止，此类模拟的挑战在于描述固体燃料在与周围气相相互作用时的运动和转化。为了解决这个问题，离散元法 (DEM) 与计算流体动力学 (CFD) 相结合，该方法允许同时跟踪所有单个反应粒子。颗粒形状由多面体表示，以近似其圆柱形几何形状。已考虑颗粒长度尺寸分布。在燃烧过程中颗粒会收缩。加热、干燥、热解和炭燃烧由颗粒的三维分辨率来解释。颗粒之间的辐射传输是根据每个颗粒的表面三角测量来计算的。模拟中考虑了颗粒炉中燃料的典型分批供给。此外，还将 13 kW 家用木屑颗粒炉的实验结果与模拟结果进行了比较。模拟揭示了水蒸气、热解气体和燃烧产物不稳定释放的细节。由于燃料供给不对称而导致燃烧器炉排上颗粒的几何分布不均匀，导致颗粒床上方的气体火焰偏转至燃烧室的一侧。这也反映在测量中。模拟很好地体现了颗粒床上方气相温度的趋势以及作为化学计量函数的平均 CO 排放量，但仍有进一步改进的空间。
This study presents an approach to simulate wood pellet combustion in domestic heating systems. Until now the challenge of such simulations lies in the description of the movement and conversion of the solid fuel while interacting with the surrounding gas phase. To tackle this problem the discrete element method (DEM), a method which allows simultaneous tracking of all individual reacting particles, was combined with computational fluid dynamics (CFD). The pellet shape is represented by polyhedrals to approximate their cylindrical geometry. Pellet length size distribution has been taken into account. Particles are allowed to shrink during the combustion process. Heating, drying, pyrolysis and char combustion are accounted for by a three-dimensional resolution of the particle. Radiative transfer among pellets is calculated based on a surface triangulation of each particle. The typical batchwise feeding of the fuel in a pellet stove has been taken into account in the simulations. Furthermore, experimental results from a 13 kW domestic wood pellet stove are compared with simulations. The simulations reveal the details of the unsteady release of water vapor, pyrolysis gases and combustion products. The non-uniform geometrical distribution of the pellets on the burner grate resulting from non-symmetric fuel feeding leads to a deflection of the gas flame above the pellet bed to one side of the combustion chamber. This is also reflected in the measurements. The trend of the gas phase temperature above the pellet bed as well as the mean CO emissions as a function of stoichiometry are well represented by the simulations, however, further room for improvement is left.