Investigations on dynamics of bubble in a 2D vibrated fluidized bed using pressure drop signal and high-speed image analysis

Abstract

In this study, we investigated the dynamic characteristics of bubbles in a vibrated airflow force field and the mechanism under which the vibration energy restrains the bubble motion in the bubble fluidization state using digital image processing and signal analysis. Through a comparative analysis of the pressure drop signal and the bubble characteristic images, the results show that the bubble coalescence causes a sudden peak value of the pressure drop signal, and fracturing causes a decrease of the pressure drop signal. When the bed is fully fluidized, the high-amplitude pressure drop signal is mainly distributed in the range of 0–12 Hz, and the amplitude range is 480–1354 Pa. During the violent bubbling of bed, the amplitude of pressure drop signal in the frequency range of 0–12 Hz decreases, and the frequency band of the high-amplitude pressure drop signal shifts to a high-frequency band. The introduction of vibration energy significantly influences on the dynamic behavior of bubbles, and when the vibration frequency is f = 20 Hz, v = 0.32 m/s, and A = 2 mm, the shape of bubbles at the bottom of the bed is mostly a flat strip and the number of bubbles is less evenly distributed, the size of the bubbles are small, the bed voidage and its standard deviation are low, and the fluidization quality of the bed is uniform and stable.