Resonant Pulsing Frequency Effect for Much Smaller Bubble Formation with Fluidic Oscillation
Resonant Pulsing Frequency Effect for Much Smaller Bubble Formation with Fluidic Oscillation
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DOI：
10.3390/en11102680
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发表时间：
2018-10
期刊：
影响因子：
3.2
通讯作者：
Pratik Desai;M. Hines;Yassir Riaz;W. Zimmerman
中科院分区：
文献类型：
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作者：
Pratik Desai;M. Hines;Yassir Riaz;W. Zimmerman
微气泡在气液接触操作中有多种应用。传统的微气泡生产在能量上是不利的，因为产生气泡所需的表面能与产生的气泡大小成反比。对于高通量低能量的系统，流体振荡器的尺寸减小了，但由于聚结，可实现的气泡尺寸受到限制。本文的假设是，可以通过改变振荡流介导的气泡形成动力学来克服这一限制。频率和幅值是振荡流中两个容易控制的因素。如果振幅足以使气泡分离，则气泡可以在频率周期的位移相位形成。如果频率过低，则会发生常规的定常流动分离机制；如果频率太高，气泡就会聚在一起。我们的假设提出了共振模式或“甜蜜点”条件的存在，通过频率调制和振幅增加，以减少聚结并产生最小的气泡尺寸，而无需额外的能量输入。这个条件被确定为一个范例系统，显示出相对大小的变化，气泡大小从稳定流动的650µm减少到振荡流动的120µm，共振条件（体积平均）的60µm，稳定流动的250µm，振荡流动的15µm，共振条件的7µm。气泡尺寸减小了10倍，而相关能量的增加最小，从而大大降低了涉及气液操作的所有过程的能量需求。该方法的能量足迹的减少在所有气液接触操作中都有广泛的影响，包括但不限于废水曝气、海水淡化、浮选分离操作和其他操作。
Microbubbles have several applications in gas-liquid contacting operations. Conventional production of microbubbles is energetically unfavourable since surface energy required to generate the bubbles is inversely proportional to the size of the bubble generated. Fluidic oscillators have demonstrated a size decrease for a system with high throughput and low energetics but the achievable bubble size is limited due to coalescence. The hypothesis of this paper is that this limitation can be overcome by modifying bubble formation dynamics mediated by oscillatory flow. Frequency and amplitude are two easily controlled factors in oscillatory flow. The bubble can be formed at the displacement phase of the frequency cycle if the amplitude is sufficient to detach the bubble. If the frequency is too low, the conventional steady flow detachment mechanism occurs instead; if the frequency is too high, the bubbles coalesce. Our hypothesis proposes the existence of a resonant mode or ‘sweet-spot’ condition, via frequency modulation and increase in amplitude, to reduce coalescence and produce smallest bubble size with no additional energy input. This condition is identified for an exemplar system showing relative size changes, and a bubble size reduction from 650 µm for steady flow, to 120 µm for oscillatory-flow, and 60 µm for resonant condition (volume average) and 250 µm for steady-flow, 15 µm for oscillatory-flow, 7 µm for the resonant condition. A 10-fold reduction in bubble size with minimal increase in associated energetics results in a substantial reduction in energy requirements for all processes involving gas-liquid operations. The reduction in the energetic footprint of this method has widespread ramifications in all gas-liquid contacting operations including but not limited to wastewater aeration, desalination, flotation separation operations, and other operations.