Abstract: Ejectors are employed for efficient mixing of gases and liquids, as well as for producing a substantial number of microbubbles. They are characterized by low equipment costs, high energy efficiency, and suitability for large-scale industrial applications. However, the current ejector techniques for microbubble production suffer from a wide distribution in bubble sizes. Moreover, the structural parameters and operational conditions of ejectors exert significant influence over microbubble size. The following patterns in microbubble size variation have been identified based on the factors mentioned above. It has been demonstrated that reducing the length and diameter of the mixing section, and increasing the angle and cross-sectional ratio of the diffusion section effectively decrease bubble size. However, the angle of the contraction section has a minor impact on bubble size. The narrowing of the range of gas bubble sizes can be achieved by a reduction in the gas flow rate and an increase in the liquid flow rate, with the bubble size exhibiting a linear relationship to the gas volume ratio. Utilizing computational fluid dynamics (CFD) simulations and particle image velocimetry (PIV) technology to investigate gas-liquid transfer mechanisms within the ejector, it is evident that efficient gas-liquid shear at the nozzle outlet of the suction chamber and within the mixing section is critical for microbubble formation, while the diffuser section is the site for bubble breakage and refinement. Furthermore, the application scenarios of microbubble production using ejectors are discussed, and future research directions are proposed.

Key words: ejectors, microbubbles, structural parameters, operating conditions, computational fluid dynamics, particle image velocimetry

摘要： 喷射器可快速实现气液混合并生成大量微气泡，且设备成本低，能效高，适用于规模化工业实践。喷射法生成微气泡的尺寸分布较宽，而喷射器结构参数及操作条件对微气泡尺寸的影响显著。基于以上因素，归纳了微气泡尺寸的变化规律：减小混合段长度和直径，增大扩散段角度、截面比可有效减小气泡尺寸，而收缩段角度对气泡尺寸影响较小；减小气体流量，增大工作液体流量可控制气泡尺寸在较小范围，气体体积比与气泡尺寸则呈线性关系。借助计算流体力学(CFD)模拟及粒子图像测速(PIV)技术对喷射器内气液间传递规律的研究，明确了接受室喷嘴出口处和混合段内的高效气液剪切是形成微气泡的关键，而扩散段是气泡破碎细化的主要场所。最后介绍了喷射器制备微气泡的应用，展望了未来研究热点。

关键词: 喷射器, 微气泡, 结构参数, 操作条件, 计算流体力学, 粒子图像测速技术