立体传质塔板罩外空间气液相流场的研究

发布时间：2018-08-05 14:33

【摘要】：作为一种新型塔板,立体传质塔板(CTST)的帽罩结构为独特的梯形立体结构,改变了传统塔板以板上液层为主要传质区域的平面型模式,将气液传质区域拓展至塔板立体空间,达到了大幅扩能增效、节能降耗的效果,在工业应用上取得了良好的经济效益。已有研究者对立体传质塔板(CTST)的帽罩内两相流动的不同特征进行了建模和模拟计算,并且获得了其液膜流动特征和液滴分布规律,但是没有对罩外空间气液两相流动进行研究,因此,本文在此基础上对立体传质塔板(CTST)帽罩外空间的气相分布和液滴粒度分布进行了研究,为塔板的进一步改进和优化奠定基础,提供了理论依据。本文建立了立体传质塔板(CTST)罩外空间流场气相分布和液滴粒度分布的数学模型。根据流场中离散液滴被气体夹带的情况,模型采用颗粒轨道模型来进行模拟;同时考虑了气体对液体的作用力、液滴自重以及虚拟质量力;对液滴的湍流扩散采用随机轨道模型进行计算。建立的数学模型有以下几个特点:①对立体传质塔板(CTST)罩外空间的气相分布和液滴粒度分布情况作了详细的分析,建立了能够准确描述罩外气相分布和液滴粒度分布的数学模型;②由于立体传质塔板(CTST)喷射罩的特殊结构,罩外的气相分布的模型的封闭采用了RNG k-ε湍流模型,罩外空间的液滴分布采用了随机轨道模型进行模拟计算,这种模型的建立更加准确的描述了罩外的流动情况;③对于液滴的粒度分布考虑了液滴的碰撞、破碎和聚并,以使模拟结果更能准确描述液滴的状态;④对常用的数值计算方法进行分析,最终确定求解控制方程的基本方法为有限容积法,差分格式选用二阶迎风格式,速度-压强关联算法采用SIMPLE算法。对立体传质塔板(CTST)罩外空间气、液相流场进行了实验研究。通过热膜测速仪测量系统和高速摄像技术对立体传质塔板(CTST)罩外流场气相速度分布和液滴粒度分布进行了实验研究,对CTST的喷射孔气速、液体流量、喷射锥角、液滴分布密度、液滴速度分布密度以及液膜速度等喷射性能进行了研究。对实验结果进行了分析,得出了喷射孔气速随板孔动能因子的变化规律及液滴的速度分布的高低两个区间,即[5°,20°]和[40°,50°]。利用计算流体力学Fluent软件对数学模型进行数值模拟,得到了罩外空间气相分布和液滴粒度的分布规律。在理论计算中,内容涵盖数值模拟各过程,包括计算选用的湍流模型、计算方法和差分格式等等,所建的模型很好地反映了气相的流动情况。根据结果,对立体传质塔板(CTST)液滴粒度分布的影响因素可以归纳为:气速、板上清液层高度、罩型以及液体的物性。另外对液滴粒径分布的研究表明,在喷射工况下,直径小于2mm的液滴占大多数,而且液滴的粒度分布更合适于上限对数正态分布函数。最后对实验研究结果与模型计算结果进行了比较。结果表明,通过实验得出的立体传质塔板(CTST)罩外空间气体流动状况的实验值与理论值是相一致的,证明了理论模型的正确性。通过对立体传质塔板(CTST)相关喷射性能的研究,得出喷射孔气速随板孔动能因子的变化规律,并得出影响液膜速度的主要因素为喷射孔气速和液膜在喷射孔上的位置的结论。
[Abstract]:As a new type of tower plate, the cap cover structure of CTST is a unique trapezoid structure, which changes the plane pattern of the traditional tray with the liquid layer on the plate as the main mass transfer area. It extends the gas and liquid mass transfer area to the tray stereoscopic space, and achieves the effect of large capacity expansion and efficiency, energy saving and consumption reduction, and obtained the industrial application. Good economic benefits. The researchers have modeled and simulated the different characteristics of the two phase flow in the cap cap of the stereoscopic mass transfer tray (CTST), and obtained the characteristics of the liquid film flow and the distribution law of the droplets, but there is no research on the gas-liquid two-phase flow in the outer space. Therefore, this paper is based on the three-dimensional mass transfer tray. The gas phase distribution and droplet size distribution in the outer space of (CTST) cap are studied. It provides a theoretical basis for further improvement and optimization of the tray. In this paper, a mathematical model of gas phase distribution and droplet size distribution in the outer space flow field of a stereoscopic mass transfer tray (CTST) cover is established. In addition, the model is simulated with a particle orbit model. At the same time, the force of the liquid, the weight of the droplet and the virtual mass force are considered, and the random orbit model is used to calculate the turbulent diffusion of the droplets. The mathematical models have the following several characteristics: (1) the gas phase distribution and droplets of the outer space of the stereoscopic mass transfer tray (CTST) cover The particle size distribution is analyzed in detail. A mathematical model is established to accurately describe the distribution of gas phase and droplet size. (2) the RNG k- e turbulence model is adopted because of the special structure of the solid mass transfer tray (CTST) jet cover, and the droplet distribution in the outer space uses random orbits. The model is simulated. The establishment of the model is more accurate to describe the flow situation outside the cover. Thirdly, the particle size distribution of the droplets is considered for the droplet collision, breakage and aggregation, so that the simulation results can describe the state of the droplet more accurately. The method is the finite volume method, the difference scheme is two order upwind scheme, and the velocity pressure correlation algorithm uses the SIMPLE algorithm. The liquid phase flow field of the three-dimensional mass transfer tray (CTST) cover is experimentally studied. The gas phase velocity distribution in the outer flow field of the solid mass transfer tray (CTST) cover is measured by the thermal film velocimeter measurement system and the high-speed camera technology. The particle size distribution of the droplet was experimentally studied. The jet gas velocity, liquid flow rate, jet cone angle, droplet distribution density, droplet velocity distribution density and liquid film velocity were studied. The experimental results were analyzed. The change law of the velocity of the jet hole gas velocity with the plate hole kinetic energy factor and the velocity of the droplet were obtained. Two intervals of the height of the cloth, namely, [5, 20] and [40, 50 degrees. The mathematical model is simulated by the Fluent software of computational fluid dynamics, and the distribution of the gas phase distribution in the outer space and the distribution of the droplet size are obtained. In the theoretical calculation, the content covers the numerical simulation process, including the calculated turbulence model, the calculation method and the difference lattice. According to the results, the influence factors of the particle size distribution of the solid mass transfer tray (CTST) can be summed up as gas velocity, the height of the liquid layer, the cover type and the physical property of the liquid. In addition, the study of the droplet size distribution shows that the droplets with the diameter less than 2mm under the injection condition are shown. The size distribution of the droplets is more suitable for the upper bound logarithmic normal distribution function. Finally, the experimental results are compared with the model calculation results. The results show that the experimental values of the air flow in the outer space of the stereoscopic mass transfer tray (CTST) cover are in agreement with the theoretical values, and the theoretical model is proved. Correctness. Through the study of the related injection performance of the stereoscopic mass transfer tray (CTST), the change law of the gas velocity with the plate hole kinetic energy factor is obtained, and the main factors affecting the liquid film velocity are the conclusion of the gas velocity of the jet hole and the position of the liquid film on the jet hole.
【学位授予单位】：河北工业大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：TQ053.5

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