螺旋转子管式光生物反应器流体动力学特性研究

发布时间：2018-05-29 10:53

本文选题：管式光生物反应器 + CFD　；参考：《北京化工大学》2017年硕士论文

【摘要】：利用微藻技术将固定碳氮、废水处理等环境保护措施与生产氢气、甲烷、柴油等生物能源相结合,已被多国政府认为是应对环境与能源危机的可行方式。在微藻技术发展中,研发高密度、低成本、易放大的微藻养殖设备——光生物反应器(PBR)是其中的重要一环,管式光生物反应器(TPBR)在这方面的优点已被广泛认可,但TPBR也存在着混合效果不好、微藻细胞易沉积、光抑制作用大等缺陷。因此,优化TPBR的结构、改善流体的流动特性、促进混合效果、提高光利用率对于提高TPBR养殖效果具有重要意义。本文对微藻技术原理、PBR的种类和结构以及影响微藻养殖的物理因素进行了较为详细的介绍,阐述了内置无源驱动螺旋转子TPBR的工作原理,应用可视化实验与CFD方法,着重分析了内置螺旋转子TPBR的速度场量、气液两相周向速度分量、旋流数、粒子运动轨迹和最大剪切力等流动特性参数,结果表明螺旋转子在促进TPBR的混合、提高光利用率等方面具有明显的作用。本文研究了转子导程、流体流速分别对内置两叶片型螺旋转子TPBR的流动特性的影响。结果显示,转子导程与液相入口流速对流动特性有不可忽视的影响,转子导程越小,螺旋转子发挥的作用越大,但剪切力也越高;因此,200mm导程的螺旋转子对养殖微藻更有优势。液相入口流速越高,转子越能促进混合及提高细胞的光暗循环频率,但剪切力也越高;所以,应优先选择大于0.3m/s小于0.6m/s的液速。气相入口流速的增加可以提高气含率,但对促进混合作用不明显。本文分析了 TPBR中的U形管部分在螺旋转子扰流作用下的流动特性,研究表明,流体经过螺旋转子时产生的旋流在到达U形管处时仍然存在,U形管的弯曲结构也可以使流体产生局部的旋流;对于内径为24mm的U型管,局部剪切力随着弯曲直径的增大具有先增大后减小的趋势。
[Abstract]:Using microalgae technology to combine environmental protection measures such as fixed carbon and nitrogen, wastewater treatment and production of hydrogen, methane, diesel and other bio-energy sources has been considered by many governments as a feasible way to deal with environmental and energy crisis. In the development of microalgae technology, the research and development of high density, low cost, easy to enlarge microalgae culture equipment-photobioreactor (PBR) is one of the important links, tubular photobioreactor (TPBR) in this area has been widely recognized the advantages. However, TPBR also has some defects such as poor mixing effect, easy deposition of microalgae cells and large photoinhibition. Therefore, it is important to optimize the structure of TPBR, improve the fluid flow characteristics, promote the mixing effect and increase the light utilization rate for improving the efficiency of TPBR culture. In this paper, the species and structure of microalgae technology and the physical factors affecting microalgae culture are introduced in detail. The working principle of TPBR with built-in passive drive screw rotor is described, and the visual experiment and CFD method are applied. The flow characteristic parameters of TPBR, such as velocity field, gas-liquid two-phase circumferential velocity component, swirl number, particle trajectory and maximum shear force, are emphatically analyzed. The results show that the helical rotor is promoting the mixing of TPBR. Improving the utilization ratio of light has obvious effect. In this paper, the effects of rotor lead and flow velocity on the flow characteristics of TPBR are studied. The results show that the rotor lead and the inlet velocity of the liquid phase have an important effect on the flow characteristics. The smaller the rotor lead is, the greater the effect of the spiral rotor is, but the higher the shear force is, so the spiral rotor with 200 mm lead is more advantageous to the cultivation of microalgae. The higher the inlet velocity of the liquid phase, the more the rotor can promote the mixing and increase the cell's light and dark cycle frequency, but the shear force is also higher. Therefore, the higher the 0.3m/s is less than the 0.6m/s 's, the better the liquid velocity should be. The gas holdup can be increased by the increase of gas inlet velocity, but the effect on the mixing is not obvious. In this paper, the flow characteristics of U-tube in TPBR under the action of spiral rotor turbulence are analyzed, and the results show that, When the fluid passes through the spiral rotor, there still exists the bending structure of the U-shaped tube when it reaches the U-shaped tube; for the U-tube with the inner diameter of 24mm, the local swirl flow can also be produced by the bending structure of the U-tube. The local shear force increases first and then decreases with the increase of bending diameter.
【学位授予单位】：北京化工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TQ033

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