不同风速下FCC颗粒和玻璃珠颗粒在扩径段内浓度波动的小波分解能量份额分布

Figure 10 shows the distribution of energy share of wavelet decomposition for the concentration fluctuation of FCC particles and glass beads particles under different apparent wind speeds in the expanding section. From Figure 10a, it can be seen that the energy share is mainly concentrated at the mesoscale, followed by the macroscale and the microscale at different radial positions, indicating that the movement of particle aggregates dominates the particle flow in the expanding section. At the mesoscale, the energy share decreases with the increase of wind speed, because when the wind speed is low, the drag force on the particles is small, making it easier for the particles to aggregate and enhance the mesoscale aggregate movement inside the tube. Meanwhile, as the radial position moves towards the center of the tube, the difference in the energy share change with wind speed at the mesoscale decreases, indicating that the effect of wind speed on the mesoscale structure movement at the tube wall is greater than that at the center of the tube. At the microscale, the energy share decreases with the increase of wind speed, indicating that under high wind speed, the particle density inside the expanding section decreases, leading to a decrease in the strength of particle collision and movement at the particle layer level. In contrast, at the macroscale, the energy share increases with the increase of wind speed, and the increase is the largest at the tube wall, indicating that the overall flow intensity inside the expanding section increases with the increase of wind speed, and the effect of the tube wall becomes more prominent. In addition, the energy share at the microscale gradually increases towards the center of the tube, indicating that the movement of particles at the particle layer level is more intense at the center of the tube than at the edge. The larger energy share at the edge of the tube than at the center indicates that under the comprehensive influence of wind speed and tube structure, the macroscopic gas-solid flow at the edge is more complex.

According to Figure 10b, the energy share distribution of glass beads at different scales is consistent with that of FCC particles. The maximum energy share is distributed at the mesoscale, followed by the macroscale and the microscale, indicating that the flow structure of the two materials is the same. Similarly, with the increase of wind speed, the energy share of glass beads decreases at the microscale and mesoscale, and increases at the macroscale. However, compared with FCC particles, the energy share of glass beads at the microscale decreases while it increases at the mesoscale or macroscale, indicating that the increase in particle density weakens the movement strength at the particle layer level, which is related to the decrease in the interaction between particles with large density. Correspondingly, the particle aggregation causes an increase in the movement strength of larger scale flow structures. At each radial position, the change in energy share of glass beads at different scales with the increase of apparent wind speed is larger in the edge and transition regions than in the center region compared with FCC particles, indicating that particles with higher density are more sensitive to wind speed during the movement process in the expanding section. Taking the energy share at the macroscale as an example, the mixed flow of glass beads and gas is more affected by the comprehensive influence of the tube structure and operating conditions than FCC particles.