Study of pore-scale coke combustion in porous media using lattice Boltzmann method
Study of pore-scale coke combustion in porous media using lattice Boltzmann method
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DOI：
10.1016/j.combustflame.2020.10.036
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发表时间：
2021-03
影响因子：
4.4
通讯作者：
Timan Lei;Zhen Wang;K. Luo
中科院分区：
文献类型：
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作者：
Timan Lei;Zhen Wang;K. Luo
原位燃烧开采稠油是一个高风险的过程，需要对焦炭燃烧前沿进行深入的认识。然而，由于焦炭燃烧动力学的复杂性，模拟焦炭的燃烧具有一定的挑战性。本文提出了一种多松弛时间（MRT）晶格玻尔兹曼（LB）方法来模拟多孔介质中固体焦炭在孔隙尺度上的燃烧过程。与单松弛时间模型相比，MRT LB模型可以提高数值稳定性。这个新的负载均衡模型比现有的负载均衡模型有两个主要的改进。首先，通过温度依赖密度考虑热膨胀效应，满足低马赫数流动条件。其次，在不使用迭代方法的情况下，分别采用源项和反弹格式对焦炭-流体界面的共轭传热和物种守恒进行了建模。通过对孔隙尺度焦炭燃烧过程的模拟，验证了所建立的LB模型的优越性能。结果表明，该模型能较好地再现焦炭燃烧动力学，并能捕捉到孔隙尺度下从流体相到固相等温线的变化。相比之下，如果不像以前的模型那样考虑热膨胀或共轭传热的影响，模拟将低估燃烧温度，甚至无法预测高驱动力引起的不稳定性。此外，利用提出的LB模型，进行了参数化研究，以评估进气和多孔结构对焦炭燃烧的影响。研究结果表明，进气温度和驱动力应控制在一定范围内，否则它们的影响可能可以忽略不计甚至是负面的。大孔隙率加速焦炭燃烧，导致理想的燃烧前沿。非均匀的焦炭分布影响孔隙尺度燃烧细节，但不影响整体燃烧强度，而随机的基体结构可能影响局部和全局的燃烧动力学。总体而言，本研究建立了一个可靠的LB模型来研究孔隙尺度焦炭燃烧，有助于完善ISC工艺开采稠油的知识库。
In-situ combustion (ISC) for heavy oil recovery is a high-risk process and thus calls for a deep understanding of the coke combustion front. However, simulations for describing pore-scale coke combustion are challenging because of complicated combustion dynamics. This study proposes a multiple-relaxation-time (MRT) lattice Boltzmann (LB) method to simulate solid coke combustion in porous media at the pore scale. The MRT LB model can enhance numerical stability compared with the single-relaxation-time counterpart. This new LB model offers two major advances over existing LB models. First, thermal expansion effects are considered via temperature-dependent density, satisfying the low Mach number flow condition. Second, conjugate heat transfer and species conservation at the coke-fluid interface are modelled by a source term and a bounce-back scheme, respectively, without resorting to iterative methods. Simulations of pore-scale coke combustion are conducted to validate the superior performance of the developed LB model. The results show that this model can reproduce coke combustion dynamics and capture variations in isotherms from the fluid phase to the solid phase at the pore scale. In contrast, without considering effects of thermal expansion or conjugate heat transfer as in previous models, simulations would underestimate the burning temperature and even fail to predict instability caused by a high driving force. Moreover, using the proposed LB model, a parametric study is performed to assess the impact of the inlet air and porous structure on coke combustion. The findings suggest that inlet air temperature and driving force should be controlled within certain ranges, otherwise their influences may become negligible or even negative. Large porosity accelerates coke combustion and leads to a desired combustion front. Heterogeneous coke distribution affects pore-scale combustion details but not the overall combustion intensity, while a random matrix structure may influence combustion dynamics both locally and globally. As a whole, this study develops a reliable LB model to investigate pore-scale coke combustion, which contributes to advancing the knowledge base for heavy oil recovery using the ISC process.