Hydrodynamics Of Gas-solid Flow Around Immersed Tubes In Bubbling Fluidized Beds Based On Image

Bubbling fluidized-bed combustion boilers are widely used in Industry. Its immersed tubes have high heat transfer efficiency and can keep the bed under a moderate temperature. However, while the tubes are absorbing the heat from the particle, it is impacted by particles constantly that cause serious erosion. So, it has a great significance to design high efficient and safe boilers that studying on hydrodynamics of gas-solid flow around immersed tubes in bubbling fluidized beds.Firstly, the image velocimetry technology was introduced. It included the theory and computational steps. Particle tracing algorithm based cross-correlation method was also introduced in this paper. Its advantage against traditional particle tracing algorithm and applied situation were also proposed.Secondly, the full field velocity distribution of particles in bubbling fluidized beds was measured under different superficial velocity , different tube arrangement and different tube pitches. Through comparison, it was found that the superficial velocity, tube arrangement (includes staggered and inline tube banks), tube pitches (includes transverse and longitudinal pitch) have significant effect on the movement of particles and bubbles. The results compared well with the previous simulation and experiment findings.Last, the images of instantaneous particle velocity got from particle tracing algorithm gave the dynamic trajectory of particles. The mixed regular was found from that. Besides, the process of particle impacting one tube and frequency of the bubbles attacking the middle tube in bottom row were investigated. It was great contribution to study the tube erosion.