| A cyclone separator is one of the most important components in a circulating fluidized bed (CFB) boiler. Its performance affects the operation of the CFB boiler directly. The pressure drop and the separation efficiency of a cyclone are the criterions to evaluate the performance of the cyclone. The effect of air leakage from a standpipe connecting to the bottom of the cyclone on the performance of the cyclone is remarkable. But reference papers on the influence of air leakage on performance of a cyclone are very few.This thesis is on cold experiments and numerical simulation of a cyclone. The effects of air leakage on the pressure drop and the separation efficiency of the cyclone were investigated in different inlet velocities and inlet solid loadings.The body diameter of the cyclone is 200 mm. The diameters of the standpipes are 56 mm and 80 mm, respectively. Experiment results show that in air flow, the pressure drop decreases with increasing the velocity of air leakage in the standpipe. In air-solid flow, the separation efficiency decreases, the pressure drop decreases and then increases with increasing the velocity of air leakage in the standpipe. Air leakage influences the flow pattern of particles in the standpipe and at the cone of the cyclone.The effect of air leakage on the performance of the cyclone was simulated with FLUENT in the same conditions of the experiments. The flow models are the Reynolds stress model (RSM) and the discrete phase model (DPM). Simulation results show that: In air flow, the pressure drop decreases with increasing the velocity of air leakage in the standpipe, air leakage weakens the air whirl in the standpipes. In air-solid flows, the separation efficiency decreases, the pressure drop decreases and then increases, with increasing the velocity of air leakage in the standpipe. Air leakage increases the concentration of particles at the cone of the cyclone.The numerical simulation results are comparable with the experiment results.
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