This study was performed to investigate the effects of L/D ratio of the nozzle on initial development and macroscopic spray behavior of diesel spray to understand the formation process of spray cone angle. Near-field and far-field spray visualization was performed for various injection pressures, and the effects of L/D ratio of the nozzle on spray cone angle were analyzed. A long-distance microscope and a CCD camera were used to obtain near-field spray images. Also, macroscopic spray development was evaluated using a high-speed camera and two metal halide lamps to compare the spray cone angle depending on L/D ratio. In the initial stage of injection, a laminar flow regime is observed, and downstream of the liquid column is deformed due to the large drag force of the surrounding gas. The area of the initial spray head, which has a small amount of momentum, becomes wider due to drag, and a strong eddy flow is formed around the deformed spray head. As the momentum of the supplied fuel increases over time, a mushroom-like structure is formed because momentum is continuously supplied at the center of the spray, while the outside of the spray head receives only drag force without providing additional momentum.

中文翻译：

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喷嘴L / D对普通铁路柴油喷雾近场发展和宏观喷雾特性的影响

进行这项研究以研究喷嘴的L / D比对柴油喷雾的初始发展和宏观喷雾行为的影响，以了解喷雾锥角的形成过程。对各种喷射压力进行近场和远场喷雾可视化，并分析了喷嘴的L / D比对喷雾锥角的影响。使用长距离显微镜和CCD相机获得近场喷雾图像。另外，使用高速相机和两个金属卤化物灯评估宏观喷雾的形成，以根据L / D比值比较喷雾锥角。在注入的初始阶段，观察到层流状态，并且由于周围气体的大阻力而使液柱的下游变形。初始喷头面积，动量小，由于阻力而变宽，在变形的喷头周围形成强烈的涡流。随着所供应燃料的动量随时间增加，形成了蘑菇状的结构，因为在喷雾中心不断地提供了动量，而喷头的外部仅受到阻力而没有提供额外的动量。