Abstract

Porous burner offers attractive advantages including high combustion performance and power ranges, and approximately zero pollutant emission. In this paper, the thermal behavior of premixed flame of a CH₄/air mixture in a porous burner was examined using an unsteady In-house CFD code with an appropriate single reaction mechanism. In this regard, to solve the transient term, an implicit scheme was used, and displacement terms were solved using the upwind methodology. Additionally, the discretized central difference was employed to solve diffusion terms. At first, the results were compared with available published data, and then the influences of various working parameters, including solid matrix conductivity and volumetric heat transfer coefficient, were investigated on the flame structure. Thermal performance of the burner is studied by varying relevant parameters within a practical range. The predicted gas temperature profile near the reaction zone is much broader than that in an adiabatic premixed flame. The effect of volumetric heat transfer coefficient on the temperature profile is investigated. The local gas temperature decreases in the reaction zone and the solid temperature increases in the preheat zone with an increase in convective heat transfer. Also, the corresponding local convective heat transfer rates for different values of volumetric heat transfer coefficient are calculated and compared. Simulation results also indicate that increasing the effective thermal conductivity of the solid will decrease the solid phase temperature downstream of the flame location. Due to high temperature gradients in the solid matrix, its effective thermal conductivity has a significant impact on the conductive heat transfer rates.

摘要

多孔燃烧器具有吸引人的优势，包括高燃烧性能和功率范围，以及几乎为零的污染物排放。本文研究了CH _{4预混火焰的热行为}/空气混合物在多孔燃烧器中使用不稳定的内部 CFD 代码和适当的单一反应机制进行检查。在这方面，为了解决瞬态项，使用隐式方案，并使用逆风方法解决位移项。此外，离散化的中心差异被用来求解扩散项。首先，将结果与现有公开数据进行比较，然后研究各种工作参数，包括固体基质电导率和体积传热系数对火焰结构的影响。通过在实际范围内改变相关参数来研究燃烧器的热力性能。反应区附近的预测气体温度分布比绝热预混火焰中的气体温度分布宽得多。研究了体积传热系数对温度分布的影响。随着对流传热的增加，反应区局部气体温度降低，预热区固体温度升高。此外，还计算并比较了不同体积传热系数值对应的局部对流传热率。模拟结果还表明，增加固体的有效热导率会降低火焰位置下游的固相温度。由于固体基质中的高温梯度，其有效导热系数对传导传热速率具有显着影响。随着对流传热的增加，反应区局部气体温度降低，预热区固体温度升高。此外，还计算并比较了不同体积传热系数值对应的局部对流传热率。模拟结果还表明，增加固体的有效热导率会降低火焰位置下游的固相温度。由于固体基质中的高温梯度，其有效导热系数对传导传热速率具有显着影响。随着对流传热的增加，反应区局部气体温度降低，预热区固体温度升高。此外，还计算并比较了不同体积传热系数值对应的局部对流传热率。模拟结果还表明，增加固体的有效热导率会降低火焰位置下游的固相温度。由于固体基质中的高温梯度，其有效导热系数对传导传热速率具有显着影响。计算并比较了不同体积传热系数值对应的局部对流换热率。模拟结果还表明，增加固体的有效热导率会降低火焰位置下游的固相温度。由于固体基质中的高温梯度，其有效导热系数对传导传热速率具有显着影响。计算并比较了不同体积传热系数值对应的局部对流换热率。模拟结果还表明，增加固体的有效热导率会降低火焰位置下游的固相温度。由于固体基质中的高温梯度，其有效导热系数对传导传热速率具有显着影响。