Abstract:

Signal analysis was used to investigate the interconnection and interaction between the subsystems in the two-phase flow system of dense-phase pneumatic conveying. Firstly, based on empirical mode decomposition (EMD), electrostatic signals of a gas-solid two-phase flow system were decomposed into several signal components, namely intrinsic mode function (IMF) and the IMF1—IMF4, which were determined as major components by comparing the energy ratios of each IMF component. Afterward, subsystems of the gas-solid two-phase flow system were identified based on the decomposition results of electrostatic signals, the distribution of particles in the conveying pipeline, and the differences in particle motion mechanisms. Finally, the relationship and interaction between subsystems were inspected by the variation regulars of the dominant frequency and variance of IMF1—IMF4, respectively. Results show that: there are four subsystems within the whole two-phase flow system in the horizontal pipeline, which are the particle-fluid mixture in the dilute-phase area, the junction area, the dense-phase area, and the wall-attached area. Subsystems are related to each other by particles traveling between them. There is also an interaction between subsystems, which is a competition between particle-dominated and airflow-dominated mechanisms, and the competition becomes more and more furious when particle suspension is weak. In contrast, the competition weakens when particle suspension is good.

Key words: empirical mode decomposition, gas-solid two-phase flow system of the dense phase pneumatic conveying, subsystems

摘要：

利用信号分析考察密相气力输送两相流系统内子系统之间的相互联系和作用。首先，基于经验模态分解（empirical mode decomposition，EMD）将密相气力输送两相流系统的静电波动信号分解成若干信号分量，即固有模态函数（intrinsic mode function，IMF），再结合各IMF分量的能量比重确定出IMF1~IMF4为主干分量。之后，结合静电信号EMD分解结果、输送管道中颗粒的分布状况及颗粒运动机理的差异性三者，明确气固两相流系统内的子系统。最后，利用IMF1~IMF4的主频和方差的变化规律，分别考察了子系统之间的联系和作用。实验结果表明：水平输送管道中的气固两相流系统可分成4个子系统，分别是稀相区、交界区、浓相区以及贴壁区内的颗粒流体组织；子系统之间依靠颗粒在彼此间游走而进行联系；同时，子系统之间也存在竞争作用，该竞争是颗粒主导和气流主导两种机制之间的竞争，当颗粒悬浮性较弱时竞争激烈，当颗粒悬浮性变好时竞争减弱。

关键词: 经验模态分解, 密相气力输送两相流系统, 子系统