图像法用于流化床颗粒混合特性的研究

利用基于相关的图像法速度测量技术,测量了小型二维气固流化床密相区颗粒运动速度分布.并提出了用颗粒速度不均匀指数来衡量流化床内颗粒的速度波动与混合.速度波动对于物料扩散与对流混合均十分重要.在流化床下部,颗粒运动速度往往低于床层表面,但速度不均匀指数则高于床层表面.在床层底部颗粒速度不均匀指数随流化床气泡产生而变化.床层内部混合以对流及扩散为主,而在床层表面,混合以对流为主.床层下部速度波动有利于颗粒在床内的扩散及对流混合.流化风量的增加可以增强颗粒的混合.针对这些结论,在流化床垃圾焚烧炉的设计中,对不同的组分选用不同的给料方式,可以促进物料在床内的混合.

Research on Mixing Character of Fluidized Bed Particles with Image Processing Technique

By measuring the velocity distribution in a two-dimension small scale gas-solid fluidized bed with image processing techniques based on cross-correlation, an uneven index was proposed to estimate the velocity fluctuation and to evaluate the mixing property in fluidizcd bed. The fluctuation of velocity plays an important role to the diffused and convective mixing of particles in fluidizcd bed. At the bottom of the dense phase, the velocity of particles is smaller than those near the ff~~ space, but the velocity fluctuation is bigger than those of the latter. The velocity uneven index at the bottom is changed with the passing of bubbles, which is beneficial to blend of materials. Mixing at the bottom is mainly composed of diffuseness and convection, while in place near free space, convection plays key role in blending. Increasing the gas velocity will be of benefit to mixing in fluidizcd bed. According to these conclusions, different feeding schemes for fluidized bed incinerator were introduced, which is important for the designing of new fluidized bed waste incinerator.