In this study, the use of light sheet fluorescence microscopic imaging is demonstrated for viewing the dynamic of atomizing sprays with high contrast and resolution. The technique presents several advantages. First, liquid fluorescence gives a more faithful representation of the structure of liquid bodies, droplets, and ligaments than Mie scattering does. The reason for this is that the signal is emitted by the fluorescing dye molecules inside the liquid itself and not generated at the air–liquid interfaces. Second, despite the short depth of field (∼200 µm) obtained when using the long range microscope, the contribution of out-of-focus light is much smaller on a light sheet configuration than for line-of-sight detection, thus providing more clearly sectioned images. Finally, by positioning the light sheet on the spray periphery, toward the camera objective, the effects due to multiple light scattering phenomena can be reduced to some extent. All these features provide, for many spray situations, good fidelity images of the liquid fluid, allowing the extraction of the velocity vectors at the liquid boundaries. Here, double frame images were recorded with a sCMOS camera with a time delay of 5 µs between exposures. A typical pressure-swirl atomizer is used producing a water hollow-cone spray, which was imaged in the near-nozzle region and further downstream for injection pressures between 20 bar and 100 bar. Furthermore, near-nozzle spray shape visualization of a direct-injection spark ignition injector was conducted, describing the disintegration of the liquid fuel and droplet formation. Such data are important for the validation of computational fluid dynamics models simulating liquid breakups in the near-field spray region.

中文翻译：

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薄板荧光显微镜成像，可实现喷雾动力学的高分辨率可视化

在这项研究中，证明了使用光片荧光显微镜成像可以高对比度和分辨率查看雾化喷雾的动态。该技术具有几个优点。首先，与米氏散射相比，液体荧光更真实地表示了液体，液滴和韧带的结构。原因是信号是由液体本身内部的荧光染料分子发出的，而不是在气-液界面处产生的。其次，尽管使用长距离显微镜时获得的景深很短（〜200 µm），但是在散光片上，离焦光的贡献要比视线检测小得多，从而提供了更多清晰地分割图像。最后，通过将轻薄纸放置在喷雾边缘上，对于照相机物镜，可以在某种程度上减少由于多种光散射现象而造成的影响。对于许多喷涂情况，所有这些功能都可以为液体提供良好的保真度图像，从而可以提取液体边界处的速度矢量。在此，用sCMOS相机记录两次曝光的图像，两次曝光之间的时间延迟为5 µs。使用典型的压力旋流雾化器产生水空心圆锥形喷雾，该喷雾在近喷嘴区域以及更下游的位置成像，喷射压力在20 bar和100 bar之间。此外，进行了直喷式火花点火喷射器的近喷嘴喷射形状可视化，描述了液体燃料的分解和液滴的形成。