Formation of Ordered Bubbles in Pulsed Fluidized Beds-A CGDPM Study

The induction of ordered bubble patterns at the bed surface or vertical direction in pulsed fluidized beds has been demonstrated in numerous studies. However, this trend was predominantly founded on empirical approaches. This study presents a regular bubble pattern of an experimental pulsed fluidized bed via a coarse-grained discrete particle model and an algorithm of density-based spatial clustering of applications with noise for bubble recognition. It was illustrated that the simulated results agreed well with experiment in identifying bubble size and wavelength. A correlation between the bed natural frequency and pulsed frequency that resembled wave-like coherence was found and could produce bed surface wave (bubble eruption) and ordered bubble distributions in the vertical direction. In addition, oscillation of gas flow comprising pulsation and constant velocity was introduced to fluidize particles, and a stable bed environment for bubble formation was effectively improved by setting steady flow at the minimum fluidization velocity and pulsed flow within 0.4 u(mf)-0.8 u(mf) as an auxiliary fluidization. Besides, increasing bed length had a minimal effect on the bubble formation while bed height, which is closely related to bed natural frequency, could define bubble behaviors. Furthermore, it is crucial to modify the pulsed frequency when augmenting the bed height with the purpose of promoting the ordered bubble distributions.