The effect of nozzle internal flow on spray atomization
The effect of nozzle internal flow on spray atomization
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DOI：
10.1177/1468087419875843
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发表时间：
2020-01
影响因子：
2.5
通讯作者：
A. Agarwal;M. Trujillo
中科院分区：
文献类型：
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作者：
A. Agarwal;M. Trujillo
喷嘴表面特征对液体射流的整体雾化行为的影响进行了分析，在目前的计算工作中，通过采用三个代表性的几何形状，即一个单一的X射线断层扫描的发动机燃烧网络的喷雾A喷嘴（未处理），样条重建的多个扫描（教育），和一个纯粹的外部流配置。后一种构型常用于基本的射流雾化研究。在数值上，两相流是基于代数流体体积方法，利用OpenFoam求解器interFoam求解的。前两种几何形状的表面特征的定量表征表明，虽然它们都具有相似的圆柱不对称性水平，但与未处理几何形状相关的喷嘴配置沿流向方向的表面特征沿着比教育几何形状大得多。对于未处理配置，这在离开孔口的流中产生大得多的非轴向速度分量，并且在喷嘴孔口下游的前几个直径中也产生更显著的液面扰动。此外，这种提高的表面不稳定水平产生短得多的完整液芯长度，即，它产生更快的初级雾化。这一发现的令人惊讶的方面是，未处理的和教育的几何形状之间的差异是O（1）μm，并且它们能够在完整的液芯长度上产生O（1）mm的效应。尽管未处理几何形状的雾化更明显，但湍流液体动能的大小与教育几何形状大致相同。这突出了平均场量的重要作用，特别是，非轴向速度分量，沉淀初级雾化。在光谱的另一端，仅外部配置在近场中具有最温和的表面扰动水平，从而导致最长的完整液芯长度。
The effect of nozzle surface features on the overall atomization behavior of a liquid jet is analyzed in the present computational work by adopting three representative geometries, namely a single X-ray tomography scan of the Engine Combustion Network’s Spray A nozzle (Unprocessed), a spline reconstruction of multiple scans (Educated), and a purely external flow configuration. The latter configuration is often used in fundamental jet atomization studies. Numerically, the two-phase flow is solved based on algebraic volume-of-fluid methodology utilizing the OpenFoam solver, interFoam. Quantitative characterization of the surface features concerning the first two geometries reveals that while both of them have similar levels of cylindrical asymmetries, the nozzle configuration pertaining to the Unprocessed geometry has much larger surface features along the streamwise direction than the Educated geometry. This produces for the Unprocessed configuration a much larger degree of non-axial velocity components in the flow exiting the orifice and also a more pronounced disturbance of the liquid surface in the first few diameters downstream of the nozzle orifice. Furthermore, this heightened level of surface destabilization generates a much shorter intact liquid core length, that is, it produces faster primary atomization. The surprising aspect of this finding is that the differences between the Unprocessed and Educated geometries are of O (1) μm, and they are able to produce O (1) mm effects in the intact liquid core length. In spite of more pronounced atomization for the Unprocessed geometry, the magnitude of the turbulent liquid kinetic energy is roughly the same as the Educated geometry. This highlights the important role of mean field quantities, in particular, non-axial velocity components, in precipitating primary atomization. At the other end of the spectrum, the external-only configuration has the mildest level of surface disturbances in the near field resulting in the longest intact liquid core length.