Study On Heterogeneous Gas-solid Flow And Cluster Dynamic Evolution By Coupling PIV Measurement And DPM Simulation

In this paper,heterogeneous flow structures in gas-solid fluidized beds were studied by coupling particle image velocimetry(PIV)technique and discrete particle simulation(DPM).The effects of operating conditions on gas-solid flow were discussed firstly.Then,the cluster identification method based on solids concentration gradient was verified further.Finally,the dynamic evolution of particle clusters was quantitatively characterized by coupling the PIV and DPM methods.Literature investigation was conducted on gas-solid two-phase flow structures,measurement methods,numerical models and cluster characteristics.On this basis,the research content of this paper was introduced briefly.the measurement principle and image processing method of the PIV technique were introduced in detail.Utilizing the PIV technique,we studied the heterogeneous flow structure in a gas-solid fluidized bed as well as the influences of operating conditions such as inlet gas flow rate,solids circulation rate and particle sizes experimentally.It is found that gas velocity has a greater influence on solids concentration and velocity distributions than solids circulation rate.Particle size distribution also has an obvious effect on solids velocity field.Paper verified the identifying method for particle clusters based on solids concentration gradient further.Utilizing the proposed method,higher identification accuracy than the Soong equation was obtained for distinguishing the dense and tiny particle clusters.An integrated research framework was established by coupling the PIV and DPM methods.The CFD-DEM model was improved with the help of the exact field data measured by the PIV.Based on the integrated method,the cluster structure and its dynamic evolution process as well as other important characteristic parameters were studied quantitatively.