Three-dimensional wireless measurement of float–sink object motions in a gas–solid fluidized bed

Tomoki Katayama, Yoko Otsuka, Shiori Saito, Shusaku Harada, Takuya Tsuji, Jun Oshitani

We developed a Lagrangian sensor system capable of wirelessly measuring the 3D motions of objects and applied
it to examine the floating and sinking behaviors in a gas–solid fluidized bed. The system consisted of a sensor
particle, comprising a 9-axis sensor and a wireless module integrated into a spherical outer shell, and three pairs
of magnetic coils. By utilizing this system, we can non-invasively measure the 3D motions of objects, which
cannot be observed from the outside. In this study, we examined the motions of objects with various densities in
the gas–solid fluidized bed. We found the similarity and dissimilarity between the float–sink motions of objects in
fluidized beds and those in liquids. The experimental results revealed that the vertical motion of an object in the
fluidized bed depends on its density and can be categorized into two distinct states: floating near the surface or
settling down at the bottom. However, within a specific range of object densities close to the apparent density of
the fluidized bed, the object exhibited complicated motions in the bed. In such cases, slight density variations
induced unpredictable changes between the floating and sinking states. The results also suggested that the
settling velocity of the objects in the fluidized bed varies with their vertical positions in the bed.

International Journal of Multiphase Flow

176

104817