基于图像法喷动床内空隙率研究

利用图像二值化方法处理图片,并采用Matlab编程实现空隙率的测量,从微观层次分析空隙率对喷动流化床内流动状态的影响。研究了颗粒粒径、喷口数量和表观气速对空隙率分布的影响。结果表明,增大表观气速使床层底部的稀相区增大,床层膨胀高度增加,空隙率也随之增加。增大颗粒粒径会增大最小临界流化速率,所以在其达到流化状态后流化床内颗粒粒径增大,床内喷动区空隙率减小比较明显。在相同条件下,与单喷口相比双喷口在床层底部附近存在合并射流,同时颗粒能到达的高度显著增加,底部两侧停滞区面积减小。结合对空隙率的分析,提出一种新的表征流化床内流化状态的参数(流化指数),可以直观地表示流化床内颗粒的流化状态。

Study on Porosity in Spouted Fluidized Bed Based on the Digital Image Analysis Method

The image binarization method was used to process the picture and the measurement of porosity was realized by Matlab programming. The effect of the porosity on the flow state in the spouted fluidized bed was analyzed from the micro perspective. The effects of particle size, nozzle number and superficial gas velocity on the porosity distribution were studied. The results showed that the dilute phase area at the bottom of the bed increased with the increase of the apparent gas velocity. Furthermore, the height of bed and porosity also increased. The minimum critical fluidization rate would increase with the increase of particle size, therefore, the particle size of the fluidized bed increased when it reached the fluidized state, and the porosity of the spouted zone decreased significantly. Under the same conditions, compared with the single nozzle, the double nozzle had a combined jet near the bottom of the bed, the height which the particles could reach significantly increased, and the dead zone on both sides of the bottom decreased. Based on the analysis of porosity, a new parameter, fluidization index was proposed, to characterize the fluidization state in a fluidized bed, and could visually represent the fluidization state of the particles in the fluidized bed.