Near-field dynamics of high-speed diesel sprays: Effects of orifice inlet geometry and injection pressure

Unveiling the near-field dynamics of high-speed and optically dense liquid fuel jets and sprays, such as velocity and turbulence intensity fields, is of great importance for successful interpretation and modeling of the spraying and combustion process in internal combustion engines. Characterizing the dynamics using conventional laser optical techniques have been difficult in the near-nozzle region where the fuel jet, ligaments, and droplets interact with visible light strongly producing severe multiple scattering and optical opacity. Here, we use a novel technique to characterize the velocity and turbulence intensity fields of the high-speed diesel sprays in the near-field by multi-exposed X-ray phase-contrast images. With the X-ray-imaging data, the effects of the orifice inlet geometry and injection pressure on the near-field dynamics of the diesel sprays are investigated. Notable features of the spray dynamics in the near-nozzle region and beyond are discussed by comparing the measurement results with the predictions of conventional gas jet theories.