چكيده به لاتين
Abstract:
The effect of different gas injection patterns on hydrodynamics of gas-solid fluidized bed has been investigated using digital image analysis in this project. This fluidized bed contains glass particles of Geldart D. Three different patterns of gas injection into the fluidized bed, including the Uniform Injection Pattern of gas into the fluidized bed (UIP), the corner oriented injection pattern of gas into the fluidized bed (CoOIP) and the center oriented injection pattern of gas into the fluidized bed (CeOIP) have been applied, and bubbles average diameter, bubble size distribution, bubbles movement patterns, distribution of mass center of bubbles at different sizes during time and bubbles induced void fraction for three different types of gas injection to the fluidized bed have been investigated. There is no significant difference in the results obtained from the mean diameter of the bubbles and the size distribution of the bubbles, although this small difference is more at the lowest velocity. Three general patterns of motion have been observed for bubbles in a fluidized bed in the study of patterns of motion of bubbles. In the results of the distribution of the mass center of the bubbles with different sizes, the differences in the lowest gas velocities are more significant and also differences between different patterns are not recognizable at higher velocities. For a lowest velocity in the pattern of gas injection toward the center of the fluidized bed, the location of the presence of small bubbles is in the central section of the fluidized bed and in the corners of the fluidized bed is less. This phenomenon is almost similar in other patterns, and with a slight difference, in the pattern of gas injection tend to the corners of fluidized bed, the location of the formation of small bubbles in the section of the corners of the fluidized bed, and also relatively similar patterns observed for medium and large bubbles. At higher velocities, the location of formation of very large bubbles is at the bottom of the fluidized bed, and its density is also increased. By comparing three different patterns of gas injection into a fluidized bed at the lowest velocity, it can be concluded that the density of the formation of very large bubbles of patterns tend to corners of fluidized bed is less than other cases, and is more in the uniform pattern of gas injection into the fluidized bed and gas injection pattern prone to the center of fluidized bed. The bubbles induced void fraction for the CeOIP pattern tends to the corners of the fluidized bed, and in the CoOIP pattern, the bubbles induced void fraction inclined toward the center of the fluidized bed, and in the UIP pattern, bubbles induced void fraction has behavior is similar to the other two patterns, but is more Similar to the CoOIP pattern.
Keywords: Two dimensional gas-solid fluidized bed, Fluidized bed hydrodynamics, Different gas injection pattern to fluidized bed, Digital image analysis
