CAS OpenIR
离散颗粒法的EMMS曳力模型及其应用
王晓赞
Subtype硕士
Thesis Advisor李飞
2018-07
Degree Grantor中国科学院研究生院
Degree Name硕士
Degree Discipline化学工程
Keyword气固流化床,离散粒子法,非均匀曳力,Emms/dp,Mp-pic
Abstract

气固流化床在过程工业中有着极其广泛的应用,其内部的两相流场是典型的非平衡、非均匀系统,存在以颗粒团聚为代表的介尺度结构,这给气固流化床的模拟带来了很大的难度。在气固两相流系统中,曳力对于流场的演变起着至关重要的作用,因此建立能够描述介尺度结构的非均匀曳力模型是解决问题的关键。以往的非均匀曳力模型多基于双流体模型发展而来,面向离散化方法的非均匀曳力模型还少有报道。本文在能量最小多尺度(EMMS)理论框架下对面向离散方法的非均匀曳力模型(EMMS/DP)进行了相关研究,并利用EMMS/DP曳力模型对多个气固流化床提升管进行模拟。最终应用该方法对航天气化炉冷模装置中的气固两相流动行为进行了模拟预测。本文各个章节的研究内容如下:第一章综述了气固流态化系统的发展过程,介绍了当前比较流行的三种数值模拟方法,并且对非均匀曳力模型的发展过程作了简要的介绍,提出了发展离散化非均匀曳力模型的必要性。第二章介绍了本文使用的颗粒轨道模型中一种粗粒化的数值模拟方法——MP-PIC方法,利用该方法模拟了两个提升管算例,模拟结果与实验值吻合很好,并对该方法的两个重要参数:网格分辨率和粗粒化参数进行了相关分析。第三章对EMMS/DP曳力模型进行了改进和发展。改进了该模型颗粒参数的生成方式并将非均匀因子与固相浓度和滑移速度进行关联以考虑介尺度结构的动态效应的影响。本章还对该曳力模型进行了发展,引入了操作条件对介尺度结构的影响,使其能够适应多种工况。最后利用改进后的曳力模型与MP-PIC方法耦合对不同气固流化床提升管、不同操作条件进行了模拟验证,模拟结果与实验值吻合很好。第四章利用改进后的曳力模型对工业航天炉实验装置进行了模拟,模拟结果可以捕捉到颗粒团聚、颗粒返混等现象,对流场整体的再现与实验现象吻合。 第五章对本文进行了总结并对以后工作提出了建议。 ;Gas-solid fluidized bed is widely used in the process industry. The flow field inside gas-solid fluidized bed is a typical non-equilibrium and inhomogeneous system, where there exists mesoscale structures e.g. particle clusters. Those make it difficult to the simulation of gas-solid fluidized bed. In gas-solid two-phase flow systems, the drag force plays an important role in the evolution of the flow field. Therefore, it is necessary to establish an inhomogeneous drag model which can describe the mesoscale structure. Most of the inhomogeneous drag models were developed based on the two-fluid model, while there is seldom report about the inhomogeneous drag model for discrete particle method. In this study, we investigate the discrete-based inhomogeneous drag model (EMMS/DP) in the framework of the energy minimization multi-scale (EMMS) theory and simulate several gas-solid fluidized bed risers with the EMMS/DP drag model. Finally, this method has been used in the prediction of gas-solid flow behavior in cold-state HT-L gasifier. The content of each chapter of this dissertation is as follows:Chapter 1 summarizes the development of the gas-solid fluidization system. Three currently popular numerical simulation methods are introduced in this chapter, and the development process of heterogeneous drag model is made a brief introduction. Finally, we propose the necessity of developing the inhomogeneous drag model for discrete particle method.In chapter 2, we introduce the MP-PIC method which is a coarse grained numerical simulation method belonging to the particle tracking model used in this dissertation. Two risers are simulated by this method and the simulation results are in good agreement with the experimental measurements. Two important parameters of this method: grid resolution and coarse graining parameters were discussed in this chapter.In chapter 3, the EMMS drag model for discrete particle method (EMMS/DP) was improved and developed. This study improves the generating method of particles information and correlates the heterogeneity index (HD) with solid concentration and slip velocity to account for the dynamic effects of meso-scale structure. Further we developed this drag model by introducing the influence of operating conditions on the mesoscale structure so that it can adapt to a variety of operating conditions. Then, different gas-solid fluidized bed risers and different operating conditions were simulated with the improved drag model. The simulation results agreed well with the experimental work.In chapter 4, the experimental device of HT-L gasifier was simulated by using the improved drag model. The simulation results can capture the phenomena of particle agglomeration and backmixing. The overall reproduction of the flow field is consistent with the experimental measurement. In chapter 5, we summarize this dissertation and provide suggestions for future work. 

Language中文
Document Type学位论文
Identifierhttp://ir.ipe.ac.cn/handle/122111/26860
Collection中国科学院过程工程研究所
研究所(批量导入)
Recommended Citation
GB/T 7714
王晓赞. 离散颗粒法的EMMS曳力模型及其应用[D]. 中国科学院研究生院,2018.
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