Numerical Simulation of Baffled Flask Flow Field and Study on Clavulanic Acid Fermentation Culture
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摘要: 提出了一种用于模拟摇瓶内气液两相流动的计算流体力学模型−旋转离心加速度模型，利用该模型成功模拟了摇瓶内的气液两相流动，并分别考察了摇瓶挡板、转速、装液量等参数对传质及剪切环境的影响。结果表明：摇瓶内加装挡板可增加气液传质能力，并且提供了更大的剪切环境；提高转速有利于提升气液传质能力，特定转速下存在提供最大气液传质能力的最佳装液量。最后，利用流场模拟结果，分析了带挡板摇瓶较不带挡板摇瓶对克拉维酸种子及其发酵培养结果更好的原因。该文方法可推广到其他品种发酵摇瓶的流场分析。Abstract: A computational fluid dynamics model for simulating gas-liquid two-phase flow in a shake flask was proposed, named the centrifugal acceleration model. The model was successfully applied to investigate effects of baffles, rotation speed and filling volume on the mass transfer and shearing environment in the shake flask flow field. The results show the presence of the baffle increases the gas-liquid oxygen transfer capacity inside the flask and provids a larger shearing environment than the unbaffled flask; Higher rotation speed is favorable for the gas-liquid mass transfer ability, and the optimal liquid volume exists for a specific rotation speed that provides the best gas-liquid oxygen mass transfer capacity. Finally, the flow field simulation results were analyzed for interpreting the better result for clavulanic acid seed and fermentation process in baffled flask. The method formed in this paper can be extended to the fermentation analysis of other products.
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Key words:
- baffled flask /
- clavulanic acid fermentation /
- CFD /
- gas-liquid flow /
- gas-liquid mass transfer
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图 2 摇瓶运动过程中发酵液流体微元受力分析
Figure 2. Analysis of the fluid micro-element force in the fermentation liquid during shake flask movement
图 4 利用本文提出的旋转离心加速度模型模拟得到的不同时刻气液流动自由表面（80 r/min）
Figure 4. Gas-liquid flow free surface at different time by the rotational centrifugal acceleration model proposed in this paper (80 r/min)
图 5 不同转速下带档板与不带挡板摇瓶中传质参数流场预测值对比（装液量600 mL）
Figure 5. Comparison of flow field prediction values of mass transfer parameters between shaker flask with baffle and without baffle at different speeds (filling volume 600 mL)
图 6 不同转速下带档板和不带挡板摇瓶中形成的气液自由表面对比
Figure 6. Comparison of gas-liquid free surface formed by shaking flask with baffle and without baffle at different rotating speeds
图 7 带档板摇瓶中不同装液量下流场参数CFD模拟预测值（摇床转速120 r/min）
Figure 7. CFD simulation prediction value of flow field parameters under different liquid loading in shaking flask with gear plate (rotating speed of shaking table 120 r/min)
图 8 带档板与不带挡板摇瓶中种子培养过程参数变化对比
Figure 8. Comparison of seed culture parameters in shaking flask with baffle and without baffle
图 9 3 L带挡板与不带挡板摇瓶中克拉维酸发酵菌丝形态（装液量650 mL，培养120 h）
Figure 9. Clavulanic acid mycelium morphology in 3 L flask with baffle and without baffle (Filling volume 650 mL, cultivation 120 h)
图 10 带档板与不带挡板摇瓶中装液量对克拉维酸发酵的影响
Figure 10. Effect of filling volume in shaking flask with baffle and without baffle on clavulanic acid fermentation
表 1 不同转速下带档板与不带档板摇瓶中平均剪切应变率（SSR）大小对比
Table 1. Comparison of average shear strain rate (SSR) in shaking flask with and without baffle at different rotational speeds
Rotational
speed/(r·min−1)Average of ${\dot{Y}\!/\!{\rm s}} $ −1 Relative
difference/%With baffle Without baffle 40 2.75 2.70 2 80 22.48 16.63 35 120 40.00 30.93 29 160 60.18 51.09 18 
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表 2 带档板和不带挡板摇瓶中不同装液量下菌丝形态对比（培养120 h）
Table 2. Comparison of mycelium morphology under different filling volume in shake flasks with baffle and without baffle (cultivation 120 h)
Filling volume/mL Mycelium morphology With baffle Without baffle 150 No mycelium ball, little broken, short and many branches,
few black intracelluar particlesMycelium ball, dyeing uniformity, few branches,
few breaks, no black intracellular particles250 No mycelium ball, little broken, short and many branches,
few black intracelluar particlesMycelium ball, dyeing uniformity, few branches,
few breaks, no black intracellular particles500 No mycelium ball, little broken, short and many branches,
few black intracelluar particlesMycelium ball, more and long branches,
few breaks, no black intracellular particles650 More broken,shorter and more branches,
more black intracelluar particlesFew mycelium ball, thin and long, with long branches,
no cavitation, few black intracelluar particles900 More broken,shorter and more branches,
more black intracelluar particlesNo mycelium ball, thin and long, with long branches,
no cavitation, few black intracelluar particles
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