Analysis of X-ray radiography in atomizing sprays

Abstract

Recent studies of spray-related flowfields using synchrotron-based X-ray radiography at the Advanced Photon Source (APS), Argonne National Lab, have produced useful results related to fuel mass. A companion article to this one analyzed X-ray phase contrast imaging and it identified several problems. Those results could potentially raise questions about radiography as well. Here, we simulate X-ray radiography using the same computational tools as before, but we reach a different set of conclusions. One important finding is the demonstration that radiography detects the total liquid mass along a line-of-sight, including both drops and intact liquid. As such, it can reveal liquid mass fraction, which is related to the spray breakup rate and gas entrainment; both critical for understanding of sprays. The potential for confusion between local signal reduction by diffraction and local signal reduction by absorption is also discussed. The issue is not unusual in such circumstances. This potential background problem can be avoided by careful arrangement of the experiment, and it is clear that it does not affect the results produced by the APS.