Simultaneous Ultra-Small-Angle X-Ray Scattering and X-Ray Transmission Measurements of a Liquid Jet in Crossflow With Film Atomization

Abstract

Aircraft atomizers generally rely on multiple physical phenomena to introduce, distribute, and mix liquid fuel with the continuous air flow. Many such devices use plain jets for high liquid flow rates and film shear atomization to encourage droplet formation. To further characterize the near-field of processes, experiments were conducted to examine multiphase development of a liquid jet issuing into a subsonic crossflow. The jet impinged on a wall and the liquid subsequently filmed and convected downstream until reaching the end of the splitter plate, where it broke up by shear forces. X-ray diagnostics were used to interrogate different regions of the flow at the Advance Photon Source at Argonne National Laboratory 9-ID beamline. The projected liquid mass distribution was measured through x-ray absorption correlations using the collimated beam. The light was conditioned for Ultra-Small-Angle-X-ray-Scattering measurements, which were collected simultaneously with the transmission signal. These transmission and scattering signals were used to compute the projected mass and path-specific surface area of the spray, which were combined to calculate Satuer mean diameter. Though the transmission is typically collected using focused beam with a finer spatial resolution during a separate experimental campaign, the near-simultaneous acquisition allowed for more accurate registration between the signals and control of the operating condition. The transmission mapping confirmed the liquid path length of the unbroken liquid jet issuing into the domain and the interaction point with the wall. The spreading and flowing of the liquid down the plate and shedding from the trailing edge of the plate revealed an order of magnitude greater liquid path length, indicating the spreading of the film. X-ray scattering results indicate surface wave formation on the liquid jet and the initial stripping of droplets from the column. Furthermore, the scattering was enhanced for droplets rebounding due to splashing from the plate. The combined signals were used to calculate the droplet diameters in the shear breakup region trailing the splitter plate. These combined measurements provide detailed breakup information to inform inputs required to initialize Lagrangian spray calculations, as well as validate high-fidelity atomization simulations.