The multiphase flow inside a diesel injection nozzle is imaged using synchrotron X-rays from the Advanced Photon Source at Argonne National Laboratory. Through acquisitions performed at several viewing angles and subsequent tomographic reconstruction, in-situ 3D visualization is achieved for the first time inside a steel injector at engine-like operating conditions. The morphology of the internal flow reveals strong flow separation and vapor-filled cavities (cavitation), the degree of which correlates with the nozzle’s asymmetric inlet corner profile. Micron-scale surface features, which are artifacts of manufacturing, are shown to influence the morphology of the resulting liquid-gas interface. The data obtained at 0.1 ms time resolution exposes transient flow features and the flow development timescales are shown to be correlated with in-situ imaging of the fuel injector’s hydraulically-actuated valve (needle). As more than 98.5% of the X-ray photon flux is attenuated within the steel injector body itself, we are posed with a unique challenge for imaging the flow within. Time-resolved imaging under these low-light conditions is achieved by exploiting both the refractive and absorptive properties of X-ray photons. The data-processing strategy converted these images with a signal-to-noise ratio of ~ 10 into a meaningful dataset for understanding internal flow and cavitation in a nozzle of diameter 200 μm enclosed within 1–2 millimeters of steel.

使用来自阿贡国家实验室高级光子源的同步加速器X射线对柴油喷嘴内的多相流成像。通过在几个视角下进行的采集以及随后的层析成像重建，就地进行在类似于发动机的工况下，首次在钢喷油器内实现3D可视化。内部流动的形态揭示了强烈的流动分离和充满蒸汽的空腔（空化），其程度与喷嘴的不对称入口角轮廓相关。微米级的表面特征（它们是制造的工件）显示出会影响所形成的液-气界面的形态。以0.1毫秒时间分辨率获得的数据揭示了瞬态流动特征，并且流动发展时标显示与原位相关喷油器的液压阀（针）的图像。由于钢注射器体内的X射线光子通量的98.5％以上被衰减，我们面临着成像其内部流动的独特挑战。通过利用X射线光子的折射和吸收特性，可以在这些弱光条件下实现时间分辨成像。数据处理策略将这些图像以约10的信噪比转换为有意义的数据集，以了解封闭在1-2毫米钢中的直径200μm喷嘴中的内部流动和空化现象。