Experimental study on spray break-up and atomization processes from GDI injector using high injection pressure up to 30 MPa
Experimental study on spray break-up and atomization processes from GDI injector using high injection pressure up to 30 MPa
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DOI：
10.1016/j.ijheatfluidflow.2013.11.005
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发表时间：
2014-02-01
影响因子：
2.6
通讯作者：
Park, Sungwook
中科院分区：
文献类型：
--
作者：
Lee, Sanghoon;Park, Sungwook
研究了30 MPa喷射压力对单液射流破碎和雾化过程的影响。为此，通过可视化和PDPA（相位多普勒粒子分析仪）实验对多孔GDI喷油器的单射流进行了表征。利用Nd:Yag激光器产生的薄光片和CCD相机捕获的一系列射流显影图像，可视化了内部结构。为了量化液滴直径和速度，除了喷雾可视化外，还进行了二维PDPA系统。通过分析喷射压力增大至30 MPa时射流内部结构图像和PDPA结果，包括液滴直径和速度分布，表征了喷射压力增大对射流破碎和雾化的影响。我们的实验结果表明，在喷射初始阶段观察到射流前缘的存在。这一现象表明，相对较大的液滴在主射流前面，然后由于液滴动量的丧失而迅速消失。此外，在所有注入压力下，当射流完全发展时，可以观察到独特的“分支状结构”。这种结构具有许多与空气夹带作用有关的反向旋转分支，并迅速分解成液滴簇和液滴。特别是，随着注射压力的增加，显示结构的时间和两个分支之间的距离都缩短了。此外，基于不同注入压力下液滴直径和速度分布的结果，我们证实了注入压力对液滴破碎起关键作用，但也存在注入压力对液滴破碎的促进作用。也就是说，将注入压力从5 MPa增加到10 MPa，再增加到20 MPa， SMD （Sauter平均直径）会线性降低约10 gm。然而，注入压力超过20 MPa时，SMD并没有显著降低。(C) 2013爱思唯尔公司版权所有。
This paper focuses on the influence of injection pressures up to 30 MPa on single liquid jet break-up and atomization processes. For this purpose, a single jet from a multi-hole GDI injector has been characterized performing visualization and PDPA (phase Doppler particle analyzer) experiments. Using a thin sheet of light generated by a Nd:Yag laser and capturing a sequence of jet development images with a CCD camera, the internal structure was visualized. In order to quantify the droplet diameter and velocity, a 2-D PDPA system were carried out in addition to the spray visualization. Analyzing the images of the internal structure of jet and the result of PDPA, including droplet diameter and velocity distribution with increasing injection pressure up to 30 MPa, the elevated injection pressure on a jet break-up and atomization was characterized.Our experimental results show the existence of a leading edge of the jet observed at the initial stage of injection. This phenomenon revealed relatively large droplets ahead of the main jet then disappeared quickly as lose the droplets momentum. Furthermore, for all injection pressures, unique 'branch-like structure' was observed when the jet was fully developed. This structure had many counter rotating branches related to the effect of air-entrainment and rapidly broken down into droplet clusters and droplets. Especially, as increased injection pressure, the time to exhibit the structure and distance between two branches were decreased. In addition, based on the results of droplet diameter and velocity distribution at various injection pressures, we confirmed that the injection pressure plays a key role in droplet break-up, but a limit in injection pressure to enhance droplet break-up also occurred. That is, increasing injection pressure from 5 to 10 to 20 MPa led to a decrease in SMD (Sauter mean diameter) linearly by approximately 10 gm. However, an injection pressure above 20 MPa, did not result in any significant reduction in SMD. (C) 2013 Elsevier Inc. All rights reserved.