不同推进式桨叶对搅拌反应器内气液两相混合特性的影响

doi:10.11949/0438-1157.20191315

摘要/Abstract

摘要：

为了研究不同推进式桨叶对搅拌反应器内气液两相混合特性的影响，以某搅拌反应器的推进式桨叶为研究对象，将搅拌聚合物简化为含5%气体的清水介质，基于螺旋桨叶片设计方法和CFD流场仿真技术，采用VOF多相流模型和RNG k-ε 湍流模型，对四种推进式桨叶内部气液两相流动进行数值分析，实现了推进式桨叶参数设计和性能优化。分析设计转速在400 r/min时的径向速度、0~18 s的时间范围内气体体积分数的变化、无量纲气体体积分数以及无量纲轴向速度，来评价四种推进式搅拌反应器搅拌性能的剪切、混合、分散。研究结果表明：变螺旋角(FDC-450-γ)非对称桨叶的流动更均匀、混合速率更快和剪切分散能力能强。通过对四种不同推进式桨叶的比较分析，为后续的研究和工程实践奠定了基础。

关键词: 推进式桨叶, 两相流, 混合特性, 计算流体力学, 搅拌器

Abstract:

A stirred reactor is a device that supplies mechanical energy to a stirred medium by obtaining a suitable flow field. It is widely used in industrial production, especially in the chemical industry, and many chemical production applications are more or less affected by the effect of stirring. Due to the lack of data on the design parameters of propeller blades at home and abroad, the profile of propeller blades is poor, and the stirring performance needs to be improved. In order to study and compare the stirring effect of several propeller blades, the propelling blade of the stirred reactor is taken as the research object, and polymerization medium of the mixing reactor is simplified to water and gas. First, the propeller blades are designed according to the design parameters. Four different types of propeller blades are designed by using different helix angles and contour shapes. Then, three-dimensional diagrams of the four propelled stirred reactors are drawn and unstructured meshing is performed according to the two-dimensional diagrams. Finally, the internal flow characteristics of the four propelled stirred reactors were simulated and analyzed by using multiple reference frames, VOF multiphase flow models, and RNG k-ε turbulence models. When the speed is 400 r/min, we qualitative analyze the distribution and uniformity of radial velocity and the mixing degree through comparing radial velocity cloud graph and the variation of gas volume fraction cloud graph from 0 to 18 s (including 0.6 s, 6 s, 12 s and 18 s). Besides we also define the dimensionless gas volume fraction and axial velocity, so 0 to 18 s (including 0.6 s, 6 s, 12 s and 18 s) hybrid rate,distribution of the gas volume fraction and the rate of change of the axial velocity are quantitative analyzed. According to the results of numerical simulation, the mixing characteristics and mixing degrees of the four types of propelled stirred reactors were compared. We can draw the following conclusions the asymmetric blades with variable spiral angle (FDC-450-γ) has a more uniform flow rate, the mixing rate is faster and the mixing degree is better. In this paper, four different propeller blades are selected for comparison and analysis, which lays the foundation for subsequent research and engineering practice.

Key words: propeller blade, two-phase flow, mixing characteristics, computational fluid dynamics, stirred vessel

中图分类号:

TQ 027

黎义斌, 宋亚娟, 歹晓晖, 李正贵. 不同推进式桨叶对搅拌反应器内气液两相混合特性的影响[J]. 化工学报, 2020, 71(S1): 227-235.

Yibin LI, Yajuan SONG, Xiaohui DAI, Zhenggui LI. Effects of different propeller blades on gas-liquid two-phase mixing characteristics in stirred reactor[J]. CIESC Journal, 2020, 71(S1): 227-235.

图/表 13

图1 推进式桨叶展开图

Fig.1 Expansion drawing of propelling blade

图2 系数ki的曲线

Fig.2 Curve of coefficient ki

表1 非对称形桨叶的横截面宽度bi的确定

Table 1 Cross-sectional width bi of asymmetric blades

r/R	(x₂/b_m)/%	(x₁/b_m)/%	(b/b_m)/%	(b₁/b)/%
0.2	28.68	46.99	75.67	35
0.3	32.67	51.24	83.91	35
0.4	36.62	54.91	91.53	35
0.5	40.53	56.52	97.05	35.5
0.6	44.18	55.82	100	38.9
0.7	46.97	52.22	99.19	44.2
0.8	48.22	44.63	92.85	47.8
0.9	45.46	30.31	75.77	50

图3 桨叶横截面图

Fig.3 Cross-section of blade

表2 四种推进式桨叶的名称简化

Table 2 Simplified names of four propelling blades

名称	表示方法	含义
恒螺旋对称桨叶	DC-450-32
变螺旋对称桨叶	DC-450-γ
恒螺旋非对称桨叶	FDC-450-32
变螺旋非对称桨叶	FDC-450-γ

图4 四种推进式桨叶的三维模型

Fig.4 Three-dimensional models of four propelling blades

图5 四种不同搅拌反应器

Fig.5 Four different stirring reactors

图6 搅拌反应器网格划分

Fig.6 Mesh generation of stirring reactor

图7 搅拌反应器的轴向力以及轴功率

Fig.7 Axial force and axial power of stirring reactor

图8 A—A横截面的气相速度云图

Fig.8 Velocity cloud diagram of gas on A—A cross section

图9 搅拌反应器在0~18s内的气体体积变化过程

Fig.9 Gas volume change process of stirring reactor in 0—18 s

图10 气体体积分数无量纲化分析

Fig.10 Dimensionless analysis of gas volume fraction

图11 无量纲速度沿轴向的变化

Fig.11 Dimensionless velocity changes in axial direction

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