Microbubble cloud generation from fluidic oscillation: underpinning fluid dynamics

90年代以来，微泡的各种生成机制得到了广泛的研究。现有技术目前被认为是文丘里方法，其泵送气体和液体。由于液体的密度通常比气体高一千倍，因此它本质上比PI最近获得专利的机制更低的能量效率，该机制产生具有高滞留率（目前可实现约40%）的孔尺度（小至20微米）的微气泡，均匀尺寸和间隔，因此非聚结，与相同流速的细气泡（1- 2 mm）相比，具有更少的能量使用的羽流。对于最小尺度的微泡，工业过程使用饱和液体释放方法（6巴压缩），其中30-60微米气泡成核，但具有高聚结速率，因此在湍流中产生非常宽范围的气泡尺寸。我们估计，我们的流体振荡方法节省了90-95%的电力，同时节省了类似的资本成本（不需要昂贵的饱和系统和大型泵来泵送饱和液体）。现场试验正在进行中，以证明用这种方法取代水净化中的固体去除系统的可行性。我们已经确定了至少25个潜在的应用和超过40家对该技术感兴趣的公司。困难的是，工业应用和工程实施超出了我们对微泡产生机制的基本理解，以及它如何取决于情况，操作条件和控制流体回路设计。我们相信，有潜在的医疗应用（药物输送，血液中的气体交换），如果该方法可以扩展到纳米级的气泡具有相同的功能的单分散性和能源效率。为了理解如何将微泡传输要求与已经确定的各种应用的流体回路和生成装置相匹配，我们必须建立作为准确预测器的计算模型，以及验证它们并在许多代表性条件下从可视化和测速研究中定性地理解动力学。以前从未使用过微泡的混合和气体转移机制是可能的。如果没有准确的工程设计工具和全面的科学理解，这些系统的实施将受到打击或错过，即使它们像我们迄今为止所有成功的应用一样工作，它们也肯定不是最佳的。由于该技术具有颠覆性，因为利用潜在的能源和资本节省来改变基础设施将推动多个行业的变革，因此在早期阶段采用的设计和实施协议变得一成不变。但是，如果实施的过程是非最优的，这些非最优性将持续至少一个资本周期。在系统工程中，有许多例子表明，设计规则已经存在了世纪（因为它们是有效的），尽管重新审视它们可以节省大量的成本。因此，这个建议是非常及时的，因为现在采用的设计缺陷可能是长期昂贵的，即使对当前实践的潜在改进是惊人的。在这个建议中，我们将承担最先进的流动可视化和测速技术，多相流和工程建模，以及一系列流体回路和由此产生的微泡动力学实验，其中一些已经由研究人员率先开发，以开发完整的工具集来设计微泡生成系统，该系统被调整到应用系统动力学。

Microbubbles received an intensive study for various generation mechanisms in the 1990s. The state of the art is currently perceived as being the Venturi method, which pumps both gas and liquid. As the density of liquids are usually a thousand fold higher than gases, it is inherently less energy efficient than the recently patented mechanism by the PI that produces microbubbles on the scale of the pore (as small as 20 microns) with high holdup (~40% is achievable currently), uniformly sized and spaced so non-coalescent, plumes with less energy use than the same flow rate of fine bubbles (1-2mm). For the smallest scale of microbubbles, industrial processes use the saturated liquid release method (6 bar compression), with nucleation of 30-60 micron bubbles, but with high coalescence rates so a very wide range of bubble sizes in a turbulent flow are created. We estimate that our fluidic oscillation method saves 90-95% of the electricity with a similar savings in the capital cost (no expensive saturation system and large pumps are needed to pump the saturated liquid). Field trials are underway to demonstrate the feasibility of replacing solids removal systems in water purification by this method. We have identified at least 25 potential applications and over 40 companies interested in the technology.The difficulty is that the industrial applications and engineering implementations are outstripping our fundamental understanding of the mechanism for microbubble generation and how it depends on the situation, operating conditions, and the controlling fluidic circuit design. We believe that there are potential medical applications (drug delivery, gas exchange in the blood) if the methodology can be extended to nanoscale bubbles with the same features of monodispersity and energy efficiency. In order to understand how to match the microbubble transfer requirement to the fluidic circuitry and generation devices for the various applications identified already, we must build computational models that are accurate predictors, as well as validating them and understanding the dynamics qualitatively from visualization and velocimetry studies under many representative conditions.Because of the extremely low cost of microbubbles produced by this methodology, mixing and gas transfer mechanisms that have never previously used microbubbles, is possible. Without accurate engineering design tools and a thorough scientific understanding, the implementation of such systems will be hit or miss and even when they work as in all our successful applications to date, they are certainly not optimal. As the technology is disruptive in that the change of infrastructure to exploit the potential energy and capital savings will drive change across several industries, the design and implementation protocols adopted at early stages become set in stone . But if the processes implemented are non-optimal, these non-optimalities will persist through at least one capital cycle. There are many instances in engineering of systems where the rules of design have not changed for a century (since they work), even though re-visiting them could achieve substantial savings. Thus, this proposal is extremely timely as design flaws adopted now may be long term costly, even though the potential improvement over current practise is breath-taking.In this proposal, we will bring to bear the state-of-the-art in flow visualization and velocimetry, with multiphase flow and engineering modelling, and a range of experimentation in fluidic circuitry and resultant microbubble dynamics, some of which has been pioneered by the investigators, to develop the full toolset to design microbubble generation systems tuned to the application system dynamics.