【作者】 郭大江；

【导师】 那永洁；

【作者基本信息】 中国科学院研究生院（工程热物理研究所） ， 热能工程， 2008， 硕士

【摘要】 旋风分离器是循环流化床锅炉的重要部件之一,它的性能直接影响着循环流化床锅炉的运行,旋风分离器阻力和分离效率是评价旋风分离器性能的主要指标。从连接旋风分离器底部排灰口的立管反窜入旋风分离器的烟气称为窜气。窜气对旋风分离器性能的影响是不利的,窜气影响旋风分离器内的流场,从而影响分离性能。但是,国内外的公开文献中有关窜气对循环流化床锅炉旋风分离器性能的影响规律的研究非常少。本论文采用冷态实验和数值模拟相结合的方法,在不同入口风速和入口固气比下,研究窜气对旋风分离器阻力、分离效率等的影响规律。冷态实验采用筒体直径200 mm的旋风分离器、立管直径分别为56 mm和80mm的实验台。实验结果表明:在单相气流下,旋风分离器阻力随窜气速度的增大而降低。在气固两相流下,旋风分离器阻力随窜气速度的增大先降低而后升高;分离效率随窜气速度的增大而降低;影响分离效率的是立管内的窜气速度,而不是窜气率;窜气会削弱立管和旋风分离器内的旋流。通过数值模拟软件FLUENT,采用雷诺应力湍流模型和离散相气固两相流模型,模拟在相同的实验条件下旋风分离器内压力、各向速度和浓度的分布规律,分析了窜气对旋风分离器阻力、分离效率等的影响规律。模拟结果表明:在单相气流下,窜气会削弱立管内气体的旋流;旋风分离器阻力随窜气速度的增大而降低。在气固两相流下,旋风分离器阻力随窜气速度的增大先降低而后升高;分离效率随窜气速度的增大而降低;窜气会使旋风分离器圆锥段内的颗粒浓度增大。实验结果和数值模拟结果基本一致。更多还原

【Abstract】 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.更多还原