碳颗粒群悬浮燃烧的全解析直接数值模拟研究

Multi-scale particle clusters widely exist in gas-solid two-phase flows laden with pulverized coal due to the complex multi-phase interaction, which makes the main form of pulverized coal combustion as particle cluster combustion. And the particle clusters significantly affect the momentum transfer，heat transfer and mass transfer between phases causing the internal mechanism being very complex. The present research on this problem is mainly limited to the formation mechanism of particle cluster in cold state, the clustering influence on two-phase motion and the development of single stationary particle cluster one dimensional combustion model. The proposed project aims at revealing the micro/meso mechanisms of the suspended char particle cluster combustion using the fully resolved direct numerical simulation (FR-DNS) method. The research contents include: an efficiency and large-scale parallel FR-DNS algorithm of gas-solid two-phase flow and combustion based on LBM-IBM-DEM coupling method, the interaction model including interphase momentum transfer, heat and mass transfer and combustion reaction, the physical and chemical mechanism of combustion affecting on particle cluster formation and evolution and the effect of the non-uniform distribution of suspended particle clusters on particle cluster combustion characteristics. The results will provide the necessary theoretical basis for the development of Engineering two-phase turbulent combustion model.

在煤粉气固两相流中由于复杂的多相作用会形成多尺度的颗粒聚团，造成煤粉燃烧的主要形态为颗粒群聚团燃烧，并且聚团的存在会极大影响相间的动量传递和热质传递，其内部机理异常复杂。目前对该问题的研究主要局限在冷态下颗粒聚团的形成机制认识及其对两相运动的影响和单个静止颗粒群一维燃烧模型的开发。本研究将以悬浮炭颗粒群的燃烧为研究对象，拟采用全尺度解析的直接数值模拟（FR-DNS）方法开展模拟研究，以期获得微观深入的机理认识。研究内容包括：基于LBM-IBM-DEM发展气固两相流与燃烧的高效大规模并行FR-DNS算法，包含动量传递、热质传递以及燃烧反应的相间相互作用规律与模型建立，燃烧反应影响颗粒群介观聚团结构成形和演化的物理化学机制，非均匀分布悬浮颗粒聚团对颗粒群燃烧特性的影响机制。研究成果将为发展工程两相湍流燃烧模型提供必要的理论基础。

悬浮颗粒群燃烧在能源动力、航天推进、化学化工等领域都具有广泛的应用背景。本项目基于浸入边界-格子玻尔兹曼方法(IB-LBM)，发展了模拟悬浮颗粒两相流的全解析并行数值模拟平台PFlows，自主突破了包括基于边界增厚的显式浸没边界计算格式、基于单步索引的高效率低存储计算方法、基于通讯隐藏的大规模GPU异构分布式并行计算技术等三大关键技术，实现了百亿网格、千GPU卡大规模并行计算。基于该自主模拟平台，开展了冷态颗粒群沉降过程的稳定性分析，研究了加压工况下密度比对冷态颗粒群沉降过程的动力学特性及其结构特性；发展了非等温颗粒两相流的数值模拟方法，开展了二维颗粒群的非等温沉降动力学特征和三维单颗粒的非等温沉降形态研究，研究了不同Gr和Re下颗粒沉降的结构特征及运动模式；发展了静止碳颗粒低马赫数燃烧数值模拟程序，与实验进行了定量对比验证，能够正确地刻画出碳颗粒在不同温度下燃烧的三种不同模式。研究成果在包括JCP、CPC等刊物上发表SCI收录论文11篇，EI收录论文6篇，授权软件著作权2个，邀请报告2次，其他国内外会议口头报告15次，并获得包括陈学俊优秀论文奖、鲲鹏应用创新大赛全国总决赛HPC赛道银奖等各种奖励8次。