PIV Measurement And Numerical Simulation Of The Hydrodynamics Of GAS-Solid In A CFB Riser

It is applied in studying the gas-solid flow pattern in the cold Circulating Fluidized Beds (CFB) boiler with the Particle Image Velocimetry (PIV). The hydrodynamics of gas-solid is obtained under different operating conditions and on numerical simulation of dense gas-solid two phase flow.The system of PIV is constructed suitable for measuring the particle movement and the flow pattern of particle clusters is visualized in the CFB. Under the low and high solid flux, this work also study the aggregate properties such as the two-dimensional shapes, velocity and existence time of clusters on several axial/radial positions. Visual images and micro-structure of various clusters are also captured using high-speed imaging under the typical operating conditions, which reveals the variability of gas-solid flow pattern under high solid concentration.In the experimental data processing, the application of MQD cross-correlation arithmetic is successful in obtaining the properties of particle velocities under different operating conditions. Under the low solid flux, the particle velocity in the whole flow field was processed by MQD in the transitional flow regions. The results show that the variation of particle velocity with the time and the influence of particle clusters in the real time. Under the high solid flux, in the dilute flow region, the particle velocity is analyzed and discussed with the variation of operating condition. It reveals the influence of different cross-section, gas velocity, the height of bed materials, particle mean sizes and solid circulation rate on the particle movement.On the basis of PIV measurement of the gas solid velocity field, the size and the numbers of particles are measured by newly developed image processing software. The results are identical with the variation of the factual size of particles. By the viable datum, the average size of particles in the cross section is calculated in the dilute phase area of Circulating Fluidized Beds (CFB) riser.We successfully apply the two-fluid model (TEM) and kinetic theory of granular flow studying the two dimensional dense gas-solid flow characteristics in the large scale circulating fluidized beds and the cold experimental system with PIV. The results of simulation are in accord with others' simulation and experimental results. In the end, we make the three dimensional simulation for the cold CFB riser, which is closer to the factual operation and this experimental results.Our work is only an attempt about the study on the application of PIV techniques and numerical simulation in the dense gas solid flow of the circulating fluidized beds. The results show that the accuracy and efficiency of the PIV techniques and numerical simulation method on the test and prediction of the hydrodynamics of the gas solid in circulating fluidized beds riser.