强旋气固流场的湍流特性、稳流与整流

发布时间：2018-06-04 20:58

本文选题：Starimand型旋风分离器 + 流场的稳流　；参考：《青岛科技大学》2015年硕士论文

【摘要】：本文采用大涡模拟的方法对Starimand型旋风分离器的强旋气固流场进行数值模拟,针对气相流场存在的紊乱涡流、“摆尾”、“返混”等影响分离性能状况,从结构方面提出改进措施,对传统型分离器增设稳流柱和防返混锥,以改善其流场、稳定涡流扰动。为验证增设稳流柱和防返混锥的稳流效果,采用数值模拟和实验研究的方式对研究对象分类别比较。分别从涡流矢量图、流场速度、压降、湍动能耗散、液体示踪对比、质点压力动态脉动测试等几个方面重点研究。通过考察增设内构件后对旋风流场的变化规律,为微米以及亚微米级颗粒捕获和旋风除尘器性能的优化提供参考,并对旋风分离器三维流场的研究提供流体力学理论依据。所做的主要研究工作有：(1)利用数学建模软件gambit2.20构造几何模型,对模型使用流体力学软件FLUENT6.2计算,具体计算方法采用大涡模拟的数值方法。分析了Starimand型旋风分离器和增设内构件的旋风分离器的三维速度场分布,压力场分布和湍动能耗散分布情况。结果表明：在相同的操作条件下进气风速为15m/s时,增设内构件后切向速度的轴对称性比较好,最大切向速度虽然降低,但分离区壁面的分离速度并未降低,能达到较好的分离效果。涡流速度矢量图中显示：稳流柱稳流、导流作用良好,降低了内旋流与外旋流交汇处,涡流紊乱的状况,规整了涡核尾端的“摆尾”现象。防返混锥的使用有效降低了灰仓内的湍动程度,大大减少了灰斗返气量。增设内构件后,湍动耗散能大幅度降低,在旋风分离器中部湍动耗散能最大降幅为77%。(2)在气相流场的基础上,通过对外旋流进行液体示踪试验发现增设稳流柱后,下行轴向速度衰减程度小,涡核尾端有足够能量向下延伸,减少了下锥体附近“摆尾”现象的发生,有效的减少了内旋流和外旋流的相互扰动,降低了湍动能量的耗散。安装导流件后,流体在旋风分离器内旋转圈数明显增多,有利于提高分离效率。(3)在相同的试验操作条件下,对比分离器使用导流件前后,质点动态压力变化、压降、总分离效率、颗粒分级效率等性能指标,结果表明,增设内构件,对于碳粉(D50=44.65微米)和粉煤灰(D50=23.30μm)颗粒的分离总分离效率提高了5%-7%,其中1-5μm粉煤灰(D50=23.30μm)颗粒平均分离效率提高了10%左右,2μm颗粒的分级效率甚至达到了75%。虽然总压降略有提高,但是旋风分离内部动态压力变化趋势平稳。表明增设稳流柱后,降低了强旋涡流间的扰动,使内旋流依托稳流柱上升,降低了下锥体附近涡流“摆尾”程度,防返混锥的应用有效降低了灰仓内的“返混”,大大提高了旋风分离器的分离性能。
[Abstract]:In this paper, a large eddy simulation method is used to simulate the strong swirling flow field of the Starimand cyclone separator. In order to improve the flow of the traditional type separation device, the current flow field of the cyclone, the "tail" and "back mixing" influence the separation performance. The improvement measures are put forward from the structure, and the steady flow column and the anti return cones are added to the traditional type separation device in order to improve its flow. In order to verify the steady flow effect of adding the steady flow column and the anti return cones, the numerical simulation and experimental research are used to compare the classification of the research objects. The research on the eddy current vector diagram, the flow velocity, the pressure drop, the turbulent kinetic energy dissipation, the liquid tracing comparison and the dynamic pulsation test of the pressure force are studied. In order to provide reference for the optimization of the cyclone flow field after adding internal components, it provides a reference for the optimization of the micrometer and submicron particle capture and cyclone performance, and provides the theoretical basis for the study of the three-dimensional flow field of the cyclone separator. The main research work is as follows: (1) using the mathematical modeling software gambit2.20 to construct the geometric model, The model is calculated by the fluid mechanics software FLUENT6.2. The numerical method of large eddy simulation is used in the calculation method. The three-dimensional velocity field distribution, pressure field distribution and turbulent kinetic energy dissipation distribution of the Starimand cyclone separator and the cyclone separator with additional internal components are analyzed. The results show that the air flow velocity under the same operating conditions is shown. In the case of 15m/s, the axial symmetry of the shear velocity is better and the maximum tangential velocity is lower, but the separation speed of the wall surface is not reduced, and the separation efficiency is not reduced. The eddy velocity vector diagram shows that the steady flow of the steady flow column is good, the flow of the inner swirl and the outer swirl flow is reduced, and the eddy current is disorganized. The use of the anti return cones effectively reduces the turbulence level in the ash bin and greatly reduces the volume of the air return. After adding the internal components, the turbulent dissipation energy is greatly reduced and the maximum turbulent dissipation energy of the turbulent flow is 77%. (2) in the middle of the cyclone separator, on the basis of the gas phase flow field, through the external swirling flow. After the liquid tracer test, it is found that the downward axial velocity attenuation degree is small and the tail end of the vortex core has enough energy to extend down, reducing the occurrence of "pendulum tail" in the vicinity of the lower cone, reducing the interaction between the internal swirl and the outer swirling flow and reducing the dissipation of the turbulent energy. The number of rotating rings in the separator increased significantly. (3) under the same operating conditions, the dynamic pressure change, pressure drop, total separation efficiency and particle classification efficiency were used before and after the diversion of the separator, and the results showed that the internal components were added to the carbon powder (D50=44.65 micron) and fly ash (D50=23.30). The total separation efficiency of the particle separation was increased by 5%-7%, and the average separation efficiency of 1-5 u m fly ash (D50=23.30 mu m) particles increased by about 10%. The classification efficiency of 2 micron m particles was even reached to 75%., although the total pressure drop was slightly improved, but the trend of dynamic pressure in the cyclone separation was stable. The disturbance in the flow makes the internal swirl depend on the steady flow column and reduce the "tail" of the vortex near the lower cone. The application of the anti return cones effectively reduces the "back mixing" in the ash bin, and greatly improves the separation performance of the cyclone separator.
【学位授予单位】：青岛科技大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TQ051.8

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