Hard X-ray fluorescence spectroscopy of high pressure cavitating fluids in aluminum nozzles

Daniel J. Duke, Alan L. Kastengren, Katarzyna E. Matusik, Christopher F. Powell

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Abstract

X-rays are frequently used to study the internal geometry of dense objects, and to measure the density of multiphase flows. However, quantitatively measuring fluid density inside a metallic object such as a high pressure spray nozzle is difficult. X-rays of sufficiently high energy to penetrate a metal object are not appreciably absorbed by the fluid inside. This requires the use of plastic or beryllium test sections, which are not suited to high pressure conditions. We present a high-energy X-ray fluorescence technique which can overcome this problem. The experiments were conducted at the 7-BM beamline of the Advanced Photon Source at Argonne National Laboratory. A hydrocarbon fluid was seeded with cerium nanoparticles. The fluid was pumped at high pressure through aluminum nozzles with inner diameters of 0.36–0.90 mm and wall thicknesses of 2–3 mm. A collimated, monochromatic 42.5 keV X-ray beam excited K-edge fluorescence from the cerium. The Kα emission lines at 34–35 keV were recorded by a cryogenic germanium detector. Changes in fluid density due to cavitation of the liquid inside the nozzle were measured by raster scanning the nozzle across the beam. A spatial resolution of 20 × 20 µm2 was achieved with a slitted beam, which was improved to 5 × 10 µm2 with X-ray focusing mirrors. The uncertainty in the path-integrated vapor fraction was 30–40 µm at 95% confidence. A limitation of this approach is that for low vapor pressure fluids, the nanoparticles increase the vapor pressure of the fluid and act as additional nucleation sites. These experiments demonstrate a path forward for measurements of multiphase flows inside metal components under conditions that are not feasible in optically accessible materials.

Original languageEnglish
Pages (from-to)69-79
Number of pages11
JournalInternational Journal of Multiphase Flow
Volume108
DOIs
Publication statusPublished - Nov 2018

Keywords

  • Cavitation
  • Fluorescence
  • Two-phase flow
  • X-ray

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