This experimental work reports, for the first time, observations of an internal flow field involving a DARPA SUBOFF afterbody design aerator body in an inside-out type of effervescent atomizer. The effect of operating parameters like air-to-liquid ratio (ALR), operating pressure, aerator orifice diameter, aeration area, and mixing chamber diameter on internal flow within the effervescent atomizer is studied. The effect of increasing ALR on the internal flow is quantified by identifying different gas injection mechanisms at the aerator orifice (into the mixing chamber) and two-phase mixing chamber flow regimes using high-speed shadowgraphy. In particular, it is observed that as ALR is systematically increased, the gas injection mechanism transits in the following sequence: single bubbling, pulsed bubbling, elongated jetting, atomized jetting, and evacuated chamber. The range of ALRs within which these mechanisms are observed are employed to draw up a flow regime map. Similar analysis on two-phase mixing chamber flow regimes yielded a corresponding regime map for internal two-phase stabilized flow in the mixing chamber. The flow regime transited from bubbly flow, to slug flow, to churn flow, and finally to annular flow as the ALR was increased. The spray characteristics (size and velocity) at the nozzle exit are reported using phase Doppler anemometry measurements. It is observed that dense-bubbly and bubbly-slug flow regimes produce stable sprays with droplet sizes in the range of 50-80 μm in the range of 0.25%-1.50% ALR.

中文翻译：

---

泡腾雾化的实验研究，第 II 部分：新型 DARPA SUBOFF 后体流线式曝气器的内部流动和喷雾特性

这项实验工作首次报告了对内向外型泡腾雾化器中涉及 DARPA SUBOFF 后体设计曝气器主体的内部流场的观察。研究了气液比（ALR）、操作压力、曝气孔直径、曝气面积和混合室直径等操作参数对泡腾雾化器内部流动的影响。增加 ALR 对内部流量的影响是通过识别曝气孔（进入混合室）的不同气体注入机制和使用高速阴影成像的两相混合室流动状态来量化的。特别是，观察到随着 ALR 的系统性增加，气体喷射机制按以下顺序转变：单次鼓泡、脉冲鼓泡、拉长喷射、雾化喷射、和真空室。使用观察到这些机制的 ALR 范围来绘制流态图。对两相混合室流动状态的类似分析产生了混合室内内部两相稳定流动的相应状态图。随着 ALR 的增加，流态从气泡流转变为团状流、搅动流，最后转变为环状流。使用相位多普勒风速测量报告喷嘴出口处的喷雾特性（大小和速度）。据观察，稠密气泡和气泡段塞流态产生稳定的喷雾，液滴尺寸在 50-80 范围内 对两相混合室流动状态的类似分析产生了混合室内内部两相稳定流动的相应状态图。随着 ALR 的增加，流态从气泡流转变为团状流、搅动流，最后转变为环状流。使用相位多普勒风速测量报告喷嘴出口处的喷雾特性（大小和速度）。据观察，稠密气泡和气泡段塞流态产生稳定的喷雾，液滴尺寸在 50-80 范围内 对两相混合室流动状态的类似分析产生了混合室内内部两相稳定流动的相应状态图。随着 ALR 的增加，流态从气泡流转变为团状流、搅动流，最后转变为环状流。使用相位多普勒风速测量报告喷嘴出口处的喷雾特性（大小和速度）。据观察，稠密气泡和气泡段塞流态产生稳定的喷雾，液滴尺寸在 50-80 范围内μm在 0.25%-1.50% ALR 的范围内。