密集颗粒物料流动特性数值模拟研究

发布时间：2018-01-04 22:25

本文关键词：密集颗粒物料流动特性数值模拟研究　出处：《中国科学院大学(中国科学院过程工程研究所)》2017年硕士论文　论文类型：学位论文

【摘要】：工业过程中常涉及到密集颗粒物料的处理,深入认识密集颗粒物料的流动特性对设计、优化和放大相关设备至关重要。本文以移动床和喷动床为研究对象,考察系统中颗粒物料的流动特性,探索现有密集颗粒物料相关本构模型的预测精度与适用性。本论文第二章采用离散单元法模拟研究了移动床中颗粒物料的卸料特性,为第三章连续性模拟结果的合理性提供验证数据。离散模拟结果表明,随着初始堆积高度的增大,颗粒物料的流型逐渐由C类漏斗流过渡到B类半整体流。漏斗流结构下,流动区特征宽度随卸料的进行呈现(增大)—恒定—减小的变化趋势。半整体流结构下,当床层高度降到某一临界值时,流型突变为漏斗流,之后流动区特征宽度呈单调递减的变化趋势。这一结果说明,移动床卸料过程中,流动区宽度与卸料历史密切相关。第三章基于连续介质模拟,考察了目前文献中代表性的颗粒粘度模型(Schaeffer、S-S和μ(Ⅰ)模型)对模拟结果的影响。模拟结果表明,对于卸料初期为漏斗流的系统,Schaeffer模型和μ(Ⅰ)模型都能预测出漏斗流流动结构,但所预测的流动区特征宽度的数值与变化趋势明显偏离离散单元法模拟结果;对于卸料初期为半整体流流型的系统,Schaeffer模型和μ(Ⅰ)模型能够预测出移动床内物料从B类半整体流向C类漏斗流的转化过程,且流动区特征宽度变化趋势与离散单元法模拟结果定量一致。对于所考察的初始堆积高度,S-S模型的预测结果始终为半整体流,明显偏离了离散单元法数值模拟的结果。第四章基于气固喷动床,进一步检验了以上三种粘度模型对模拟结果的影响。模拟结果表明,μ(Ⅰ)模型预测得到的喷泉区高度、平局空隙率以及喷动区轮廓更接近于实验结果;Schaeffer模型得到的床层压降最接近实验测量值。三种粘度模型在喷泉区与喷动区内的预测结果差异不大,但在环隙密相区内μ(Ⅰ)模型的模拟结果明显优于其他模型。综合考虑,相较于Schaeffer与S-S模型,μ(Ⅰ)模型在喷动床预测中显示出更大的优越性。
[Abstract]:Industrial process often involves dealing with dense granular materials, the flow characteristics of dense granular materials for in-depth understanding of the design, optimization and scale-up of related equipment is very important. Based on the moving bed and spouted bed as the research object, the flow characteristics of granular material inspection system, to explore the forecasting precision and applicability of existing dense granular material constitutive correlation model. The second chapter of this paper studied material characteristics of unloading particles in the moving bed by discrete element method to provide validation data for the third chapter the rationality of continuous simulation results. The simulation results show that the discrete, with the initial accumulation height increases, particles flow gradually from the C class to the B class half funnel flow transition the whole flow funnel flow structure, flow characteristics of the width of unloading presented the trend of decrease (increase) - constant. Semi integral flow structure, when the height of bed down To a critical value, the flow pattern mutation funnel flow after flow region characteristic width monotonically decreasing. This result shows that the moving bed unloading process, flow zone width is closely related with the discharge history. The third chapter is based on the simulation of continuous medium, the effects of particle viscosity model at present in the literature on behalf of the (Schaeffer, S-S and (I) model) influence on the simulation results. The simulation results show that the system for early discharge funnel flow, Schaeffer model and mu (1) model can predict the flow structure of funnel flow, but the value and trend of flow characteristics predicted by the apparent width from the discrete element method simulation results; system for discharging the early semi integral flow, Schaeffer model and mu (I) model is able to predict the movement of materials in the bed from the B class to the C class of semi integral funnel flow transformation process, and the flow characteristics of wide area The degree of variation and discrete element method simulation results agree quantitatively. For the initial investigation of the pile height, the prediction result of S-S model is always half the overall flow, significantly deviated from the numerical simulation of discrete element method. The fourth chapter is based on the gas-solid spouted bed, to further test the effects of the above three kinds of viscosity model of simulation results simulation results show that u (I) models to predict the fountain height, draw air void and spout contour is more close to the experimental results; the pressure drop of the bed Schaeffer model can get the most close to the experimental values. Three viscosity model in the fountain area and spouted zone prediction results had little difference, but in the ring gap in the dense phase zone. (I) the simulation results of the model is better than the other models. Considering, compared with Schaeffer and S-S model, u (I) model in the spouted more advantages show bed prediction.

【学位授予单位】：中国科学院大学(中国科学院过程工程研究所)
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TQ021.1

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