非对称高速撞击流反应器内流动特性的实验研究和数值模拟

发布时间：2018-05-09 07:06

本文选题：PIV + LES　；参考：《北京化工大学》2015年硕士论文

【摘要】：目前国内外的研究越来越多的集中在过程强化以及新型反应装置的设计上面,其中限定式撞击流反应器(CIJRs)能够为反应体系提供优良的传递特性和混合效果,撞击流已广泛的应用于燃烧,吸收,干燥,解析,萃取以及纳米制备等工业生产中,然而流体在非对称CIJRs内的流动特性还没有得到充分的研究,尤其高Re体系。本实验主要研究非对称(3-4 mm)反应器在不同流速下(Re=17596-45309)的流动特性,通过2DPIV技术获取平均速度分布、湍动能分布、驻点偏移规律等。在各向同性的假设下,湍动能的计算利用两个方向的速度进行计算,通过PIV实验与LES模拟的对比验证了模拟的可靠性。基于实验与模拟的结果,研究表明：瞬态流场和驻点位置每时每刻都在一定的范围内波动,而且实验与模拟的驻点位置分布均满足正态分布,实验驻点位置波动范围较模拟偏大,这与脉动速度在入口处偏大这一显现是相一致；在Re=17000-45000之间,只要保证入口充分的发展状态,恒定的Re比,Re大小对流体的平均速度U,V,W分布、脉动速度分布和湍动能速度分布影响不大；在只改变轴线上方空间H的条件下,较大的上方空间更有利于增强传递的效果,较低的上方空间对驻点位置偏移的影响显著；在只考虑速度比影响的条件下,流速比对无因次的驻点位置偏移影响显著,10%的流速比的波动将会造成35%驻点偏移量,在反应器的中间位置流体的混合效果最好,因此有必要确保两流体入口流速比以保证流体相撞在反应器的中间位置,这些针对撞击流流动特性的研究为将来反应器的设计以及装置优化提供了基础的数据。
[Abstract]:At present, more and more researches at home and abroad focus on process strengthening and the design of new reaction equipment, in which the limited impinging flow reactor CIJRs can provide excellent transfer characteristics and mixing effect for the reaction system. Impingement flow has been widely used in combustion, absorption, drying, desorption, extraction and nanocrystalline preparation. However, the flow characteristics of the fluid in asymmetric CIJRs have not been fully studied, especially in the high re system. In this experiment, the flow characteristics of an asymmetric reactor at different velocities were studied. The average velocity distribution, turbulent kinetic energy distribution and stationary point migration were obtained by 2DPIV technique. Under the assumption of isotropy, the turbulent kinetic energy is calculated by two directions of velocity, and the reliability of the simulation is verified by comparing the PIV experiment with the LES simulation. Based on the experimental and simulation results, it is shown that the transient flow field and the stationary point position fluctuate in a certain range at every moment, and the distribution of the experimental and simulated stationary point positions satisfies the normal distribution. The fluctuating range of the experimental stationary point is larger than that of the simulation, which is consistent with the phenomenon that the pulsation velocity is larger at the entrance, and between the Re=17000-45000, the constant re ratio to the average velocity of the fluid is U / V / W distribution, as long as the sufficient development state of the inlet is ensured, and the constant re ratio is larger than the re ratio to the average velocity of the fluid. Under the condition of only changing the space H above the axis, the larger upper space is more favorable to enhance the transfer effect, and the lower upper space has a significant effect on the migration of the stationary point. Under the condition of considering only the effect of velocity ratio, the fluctuation of velocity ratio of 10% to 10% will result in 35% migration of stationary point, and the mixing effect of fluid in the middle of the reactor is the best. Therefore, it is necessary to ensure the inlet velocity ratio of the two fluids to ensure the collision position of the fluid in the middle of the reactor. These studies on the impinging flow characteristics provide the basic data for the design of the reactor and the device optimization in the future.
【学位授予单位】：北京化工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TQ021.1

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