【作者】 陶京平；

【导师】 王立新；

【作者基本信息】 青岛科技大学 ， 化学工程， 2009， 硕士

【摘要】 为了探索新型清晰切割分级方法,本文以Stairmand型旋风分离器为对象进行了窄进料分级性能的模拟与实验研究。模拟软件采用FLUENT6.2,气相流场选用k-εRealizable模型,颗粒相采用随机轨道模型。实验设备直径0.1m,进口气速6～15m/s,物料选用碳酸钙颗粒,粒径在0.1～36μm之间。本文所做主要研究工作如下:⑴以切割粒径理论为基础,建立了求解d50的理论模型,其计算结果与实验结果的变化趋势基本一致。⑵利用FLUENT6.2对其内部流场进行了数值模拟,分析了窄进料轴向位置、径向位置、进料速率、主体气速、湍流模型、湍流度对采用窄进料操作的旋风分级器分级的影响。结果表明:与全进料方式相比,窄进料能够得到更高的分级效率和更好的分级精度,但提高不大。⑶利用相间耦合的随机轨道模型对窄进料操作的旋风分级器内的颗粒运动行为进行模拟,预测了不同粒径颗粒的运动轨迹,寻找颗粒相运动行为与流场的相互影响规律,阐述了窄进料分级的原理。结果表明,“短路流”、灰斗颗粒“返混”、“上灰环”等非理想因素是造成窄进料操作分级精度不高的主要原因。⑷实验考察了主体气速、进料方式及入口质量浓度等参数对分级的影响。结果表明:主体气速与进料速率差别不大时,分级效率和分级精度较高。就分级精度与分级效率而言,窄进料比全进料略好,而点进料最好。随着入口质量浓度的增大,分级精度与分级效率降低。分级次数的增加可以提高分级效果。⑸介绍了文丘里管进料的结构及分散机理,理论分析了文丘里管的进料原理,并且采用FLUENT软件对文丘里管内部的速度矢量、静压分布进行了模拟,进一步揭示了文丘里管进料原理。⑹改进了原有分级设备,对其内部流场进行简单模拟,分析了其y=0纵剖面的静压、动压、速度等高线分布图及速度矢量、颗粒运动轨迹分布图。⑺模拟了DS型、MC型与日本专利粉体分级机的内部流场与颗粒运动行为,分析了三种分级机y=0纵剖面的静压、动压、速度等高线分布图及速度矢量、流体迹线、颗粒运动轨迹分布图。更多还原

【Abstract】 In order to develop new-type clear-cut classification method,the classification performance of a stairmand cyclone separator was studied with narrow feeding by simulation and experimentation.The gas flow field and particle track were simulated using FLUENT6.2 by k-εRealizable model and discrete random walk model respectively.The diameter of equipment is 0.1m,and gas velocity of inlet is 10m/s with the particle size range from 0.1μm to 36μm.The works are as following:(1) It was derivated the model of solving d50 on the basic of cut size theory. Theoretic computation and experimental results was inconsistent. The reason was that the influence of cone height on the critical size was not considered and the internal flow field of classifier was considered incompletely enough.(2) The internal flow field was simulated with FLUENT6.2.It was analyzed that the influence of the narrow feeding position and feeding rate and the main gas velocity and turbulence model and turbulence intensity on the collection efficiency in cyclone-classifier with narrow feeding operation. The computational and experimental results illustrated that the collection efficiency and classification precision of narrow feeding is higher than that of total feeding,but the change is small.(3) The moving behavior of solid particles in the cyclone-classifier with narrow feeding operation was simulated with discrete random walk model.The tracks of particles of different sizes was predicted.The interaction law between particles moving behavior and field was found.The classification principle with narrow feeding and the main reason of low classification precision were elaborated vividly. It was shown by particle track simulation results that the upside short circuit flow near vortex finder and the downside dust whirl in dust duct reduce classification precision and collection efficiency.(4) The influence of the main gas velocity and feeding method and inlet concentration on classification precision and collection efficiency were experimental studied.The results showed that classification precision and collection efficiency were high when the main gas velocity was close to feeding rate. Compared with classification results,the point feeding was best and the narrow feeding was better and the total feeding was worst. With inlet concentration increasing,the classification precision and collection efficiency were reducing.The bigger number of classifying times improves the classification effect.(5) The feeding structure and dispersion mechanism of the Venturi tube was Introduced.The internal velocity vectors and static pressure distribution in the Venturi tube were simulated used by Software of FLUENT6.2.The feeding Principle of Venturi tube was further revealed.(6) The original equipment was improved.Its internal flow field was simulated simply.The static pressure and dynamic pressure and velocity contours and velocity vector and particles moving trajectory distribution were analyzed simply at y=0 section.(7) The internal flow field and particles moving behavior of the DS-type classifier and MC-type classifier and powder classifier of Japanese patent were introduced and simulated simply.The static pressure and dynamic pressure and velocity contours and velocity vector and path lines and particles moving trajectory distribution in the three type classifiers above were analyzed simply at y=0 section.更多还原