气固流态化流型的混沌辨识机制研究

Fluidization pattern and its transition information have important reference value for the design and operation control of fluidized bed. By theoretical analysis with two-phase fluid mechanics, cold model experiments and chaotic dynamics analysis of transient flow signal from fluidized bed, various flow patterns and their revolution characteristics will be studied. By adjusting the size of the bed, the particle properties and the operating parameters, the cold experimental setup will reproduce a variety of flow structure. Then the flow pattern evolution in fluidized bed with changing of operating conditions will be directly observed by Capacitance Tomography Technology (ECT).Pulsating information of the transient pressure and the concentration in different flow pattern will be measured using multi-channel pressure sensor and fiber-optic probe and the signals will be denoised by the second generation wavelet. Chaos analysis method will be applied to analyze the timing signal in order to summarize the various factors affecting the bed flow pattern transition, and to explain the physical nature of the diversity flow pattern in gas-solid fluidized bed and impact mechanism on flow pattern transition from chaotic dynamics perspective. Finally, a new chaotic index can be extracted from phase plane invariants graphics to identify the flow pattern (including some typical sub-flow pattern) of gas-solid fluidization. The result of this project can provide theoretical guidance for the optimization of industrial fluidized reactor design and operating, also it can help to deepen the understanding of the nature of multiphase flow.

气固流化床流型及其转变信息对于流化床的工业设计和运行控制有重要参考价值。本项目拟通过两相流理论分析、冷态模型实验和对瞬态流动信号的混沌动力学分析，对流化床各种流型结构及其演变特性进行深入研究。通过调整床型尺寸、颗粒性质、操作参数在冷态实验台上再现各种流型结构，利用电容层析成像技术（ECT）直接观察不同操作条件下床内流型的演变历程；利用多路压力传感器、光纤探头测得不同流型下床内局部压力、浓度脉动信息，并采用二代小波对测得的信号进行去噪；用混沌分析方法对测得的时序信号进行分析，总结出影响床内流动结构变化的各种因素，并从混沌动力学的角度阐释气固两相流流动结构多样性及影响流动状态变化的物理本质；最后从混沌理论中的相平面不变量图形上提取新的辨识气固流态化流型（包括某些典型亚流型）的混沌特征指标。本项目研究可为工业流态化反应器的优化设计和控制运行提供理论指导，也有助于加深对多相流本质的理解。

气固流化床因其流-固相界面积大，传热、传质速率高，操作范围广等优势在众多不同的工业过程应用广泛。气固流动状态决定流化床中气固的混合、传热和传质行为，对流化床装置的最优设计、有效放大、高效稳定的运行和状态监测十分重要。本课题在不同尺寸的冷态流化床实验装置上，采用压力传感器和光纤颗粒浓度测量仪分别测量了床内不同位置的压力和局部空隙率动态信号，应用时域分析、频域分析和混沌分析等多种时间序列分析方法，从波动信号中提取了反映床内流动状态的特征量。研究了表观气速、颗粒粒径、静床高度和床尺寸等因素对各特征量的影响规律，建立了特征量与床内流动状态的定性联系。采用数码摄像机捕捉流化床内气泡行为的变化，建立直观的物理现象与抽象的特征量之间的联系，帮助对实验结果的理解和分析。本课题的研究成果加深了对流化床内流动状态的理解，为实现采用波动信号定量表征流动状态和对流动状态的实时在线监测打下了基础。项目执行期间共发表SCI论文14篇，EI论文3篇，国际会议论文3篇，培养博士研究生3名，硕士研究生3名。