【作者】 曹晴云；

【导师】 金有海； 王建军；

【作者基本信息】 中国石油大学 ， 化工过程机械， 2008， 硕士

【摘要】 旋风分离器作为循环流化床锅炉中重要的气固分离设备,其性能的好坏直接影响到整个循环流化床锅炉的出力、效率及运行寿命。为了使该设备更好地服务于生产实际,本文采用商用CFD软件FLUENT对直切式旋风分离器内的气相流场进行了数值研究。结果表明:雷诺应力湍流模型对气相流场的计算与实验测量结果基本相符,有较高的预报精度;旋风分离器入口结构的非轴对性以及气相旋流的不稳定性造成气相流场呈非轴对称性,主要表现为气流旋转中心与分离器几何中心不重合;排气管内切向速度呈强旋流状态,轴向速度呈强剪切流特征,这些都是造成排气管内产生流动阻力的重要原因。同时还研究了入口面积比K A、排气管直径比d~r、排尘口直径比d~c、入口速度Vi和温度T等结构参数和操作条件对气相流场的影响规律,为旋风分离器的结构优化提供了参考依据。最后,在气相流场模拟的基础上,引入颗粒随机轨道模型,计算了颗粒的运动轨迹。结果表明,分离器内颗粒的运动情况非常复杂,并且带有很大的随机性。对于细小颗粒,上行流夹带是影响效率的主要因素,其次是短路流和排尘口返混;对于粒径较大的颗粒,影响效率的主要因素是顶灰环和排气管短路流。以上研究结果对于旋风分离器分离机理的研究具有一定的参考价值。更多还原

【Abstract】 The cyclone separator is one of the most important components in CFB boilers. Its efficiency is vital for the proper operation of the boiler. In order to make the equipment serve the industry better, the gas-phase flow filed in the cyclone separator was numerical studied by using the commercial software FLUENT. The simulation results based on the Reynolds stress model are in good agreement with the measured results. The results show that the gas flow filed is asymmetric due to the asymmetry of the inlet structure and the unstable characteristics of the swirl flow, and the vortex center of the gas flow is deviated from the geometrical center of the cyclone; the high gas swirling intensity and shear flow characteristics of the axial velocity in the vortex finder are contributed to the energy loss. Besides, the effects of the structural parameters and operating conditions on the gas phase flow were studied to provide references for the design and operation of cyclone separator, including the area ratio of cyclone cross-section to inlet section (KA), the diameter ratio of the vortex finder to the cyclone ( d~r ), the diameter ratio of the dust discharge to the cyclone ( d~c ), inlet velocity ( Vi ) and temperature (T). Finally, on the basis of the gas flow field, solid particle trajectories were simulated by using the two-way coupling lagrangian scheme. The results show that particle motion is very complex and has a great randomness. For the fine particles, the main factors influencing the efficiency are the air entrainment in the inner vortex region, short-circuit flow near the vortex head and re-entrainment at the bottom of discharge cone. For the larger particles, the main influencing factors are“upper dust ring”near the top plate and short-circuit flow near the vortex head. The above results have a certain reference value for the research on the separation mechanism of cyclone separator.更多还原