Study On Gas-solid Two-phase Hydrodynamics In Flat-bottomed Spouted Bed Based On Image Method

The porosity is an important parameter in the two-phase flow system.It is important to understand the distribution of the porosity and the physical mechanism of the two-phase flow pattern.In this paper,the binarization method is used to process the images.The porosity is measured by MATLAB programming.Analyzed the influence of the porosity on the flow state in the spouted fluidized bed from the micro perspective.The effects of particle size,the number of nozzles and superficial gas velocity on the porosity distribution were studied.The results show that increasing the superficial gas velocity will cause the dilute phase zone at the bottom of the bed to become larger and the expansion height of the bed to increase,and the porosity will also increase.Increasing the particle size will increase the minimum critical fluidization rate.Under the same wind speed,the particle size of the fluidized bed increases,and the porosity of the spout zone in the bed decreases more obviously and does not show obvious fluidized state.Compared with the single nozzle,the double nozzle has a combined jet near the bottom of the bed,and the height of the particle can be increased obviously.And the dead zone on both sides of the bottom is decreased.In addition,fluidization index,which is a parameter to characterize the state of fluidization in the fluidized bed,is proposed in this paper based on the analysis of the porosity.It can intuitively show the fluidized state of the particles in the fluidized bed.This paper focuses on the bubble generation process to study the hydrodynamic parameters of the bubble phase,in-depth analysis of the fluidized bed porosity and axial heterogeneity.The simulation results are compared with the experimental data obtained by the image method,which shows the interaction between bubbles and void fraction.Bubble from generation to growth and then to the rupture process always accompanied by changes of the porosity.From the bubble point to analyze the distribution of porosity in the spout bed,you can intuitive observe the porosity distribution in the fluidized bed.According to the flow characteristic of particles in the spouted fluidized bed,two soft-sensing methods,multi-step linear regression and support vector machine(SVM),are proposed.In the process of modeling,the influence of each parameter on particle flow was considered.And the methods of the auxiliary variables and data preprocessing were determined.The results show that the prediction accuracy of multi-step linear regression method is better than that of SVM by predicting the data in numerical simulations.