解决网格的矛盾需求：面向固体燃料颗粒燃烧模拟的网格无关的欧拉-拉格朗日方法-CEJ-Zhang2020

题目：面向固体燃料颗粒燃烧模拟的网格无关的欧拉-拉格朗日方法
摘要: 在这项研究中，利用基于层的热厚颗粒模型，开发了具有三种粗粒化算法（coarse graining algorithms）的计算流体动学（computational fluid dynamics, CFD）模型。本文实现了三种气固耦合方法：立方平均法（cube averaging method, CAM），两网格方法（two-grid method, TGM）和基于扩散的方法（diffusion-based method, DBM），将这些耦合方法应用于单个生物质颗粒燃烧的仿真，并与广泛使用的质点法（particle centroid method, PCM）进行了对比。结果表明，PCM对网格大小有很强的依赖性，而CAM和TGM不仅与网格无关，而且还提高了仿真的准确性。同时，引入了一个新参数，即耦合长度。此参数影响颗粒子模型所需的气相参数的采样以及固相参数的分布规律。本文给出了一种利用经验相关性估计耦合长度的方法。通常，过小的耦合长度会低估加热速率和脱挥发分速率，而过大的耦合长度会高估颗粒表面的氧气浓度。此外，耦合长度也影响气相产物的分布。
亮点: 1. 提出了一种模拟热厚颗粒燃烧的粗粒化CFD方法；2. 所实施的算法通过单颗粒实验验证；3. 研究了粗粒化算法中的参数。
关键词: CFD; 固体燃料; 欧拉-拉格朗日耦合; 燃烧
关键问题：欧拉-拉格朗日方法对于网格的矛盾要求，用于气相的网格必须足够细，以使控制方程的解与网格无关，而颗粒子模型要求网格尺度应远大于颗粒尺寸，可以进行适当的平均以获得相间性质，例如孔隙率及局部气相的理化性质。
图片摘要

欧拉相和拉格朗日相之间的耦合关系/Coupling between Eulerian and Lagrangian frameworks.

Title: Grid-independent Eulerian-Lagrangian approaches for simulations of solid fuel particle combustion
Abstract: In this study, a computational fluid dynamics (CFD) model with three coarse graining algorithms is developed with the implementation of a layer based thermally thick particle model. Three additional coupling methods, cube averaging method (CAM), two-grid method (TGM) and diffusion-based method (DBM), are implemented. These coupling methods are validated and compared with the widely used particle centroid method (PCM) for combustion of a biomass particle in a single particle combustor. It is shown that the PCM has a strong dependence on the grid size, whereas the CAM and TGM are not only grid independent but also improve the predictability of the simulations. Meanwhile, a new parameter, the coupling length, is introduced. This parameter affects the sampling of the gas phase properties required for the particle model and the distribution of the solid phase properties. A method to estimate the coupling length by using empirical correlations is given. In general, it is found that a too small coupling length underestimates the heating-up rate and devolatilization rate, while a too large coupling length overestimates the O2 concentration at the particle surface. The coupling length also has an influence on the distribution of the gas phase products.
Key words: CFD; Solid fuel; Eulerian-Lagrangian coupling; Combustion
原文链接, Chemical Engineering Journal, IF: 8.355