Abstract:Bubble behavior plays a decisive role in hydrodynamic properties and bed characteristics such as heat transfer, mass transfer in gas-solid fluidized bed. The dynamic characteristics of bubbles are important parameters for the simulation and design of a gas-solid bubbling fluidized bed reactor. Acoustic energy has the effect of promoting the particle movement and bubble breaking, which changes the dynamic behavior of bubbles, thus improving the fluidization state as well as the heat and mass transfer characteristics of gas-solid fluidized bed. Therefore, studying the influence of sound waves on the dynamic characteristics of bubbles is helpful to comprehend the acoustic fluidized bed. The glass beads with an average diameter of 55 μm were employed as raw materials in a half-cylindrical fluidized bed with a diameter of 120 mm. A gas-solid two-phase flow bubble measurement system with dual optical fiber probe was developed for measuring the bubble movement in the gas-solid fluidized bed. Four parameters of bubble fraction, bubble frequency, the average chord length and the mean rising velocity of bubbles at different fluidizing gas velocities were tested. Besides, the bubbling characteristics of an acoustic fluidized bed was further analyzed using the dual optical fiber probe. It was observed that the effect of sound wave on the behaviors of bubbles and the fluid dynamics properties of bubbles were related to the fluidizing gas velocity. Given a fixed sound frequency, the bubble fraction, frequency, the average chord length and the mean rising velocity of bubbles decreased with the increase of sound pressure level at low fluidizing gas velocity. While at high fluidizing gas velocity, the bubble fraction and frequency increased with the increase of sound pressure level, the average chord length and the mean rising velocity of bubbles decreased with an increase of sound pressure level. Given a fixed sound pressure level, the bubble fraction, frequency, the average chord length and the mean rising velocity of bubbles decreased first and then increased with the increase of sound frequency at low fluidizing gas velocity, reached the minimum value at about 80 Hz. While at high fluidizing gas velocity, the bubble fraction and frequency increased first and then decreased with the increase of sound frequency, reached the maximum value at about 80 Hz. The average chord length and the mean rising velocity of bubbles decreased first and then increased with the increase of sound frequency, reached the minimum value at about 80 Hz.