Three Dimensional Mass Fraction Distribution of a Spray Measured by X Ray Computed Tomography

Abstract

In order to design a spraying system with the desired characteristics, the atomization process has to be understood in detail, including the primary breakup of the liquid core. Accurate prediction of primary breakup is a major barrier to computerbased analysis of spray combustion. The development of models is hindered by the lack of validation data in a region where the fluid is dense, and optical access is therefore limited. The present experimental study is aimed at probing the spray structure by means of Xray computed tomography (CT). A fullcone atomizer (0.79 mm orifice diameter) spraying in air at ambient pressure is investigated as a proof of concept. A mixture of water and iodine is used as the working fluid, providing elevated Xray absorption and therefore, improved signaltonoise ratio. Several hundreds of Xray projections are acquired as the spraying atomizer is rotated in front of the detector. Standard software for medical imaging is used to reconstruct the threedimensional timeaveraged distribution of liquid mass fraction in the full field of view, from the intact liquid core to the dilute spray region. A spatial resolution of 0.6 mm is obtained along the spraying direction, while the resolution is 0.3 mm in the other two directions. Significant asymmetries in the structure of the spray are revealed.