Simultaneous neutron radiography of metal nozzle geometry and near-field spray

Spray flows are prominent in aerospace fuel systems, but their complexities are not fully understood, therefore various nonintrusive probes can be used to study objects and processes without modifying or destroying them and have been applied to measurement of spray characteristics. Such imaging probes include well-known X-ray techniques and to some extent less well-known neutron methods, which are particularly useful for the study of flows inside spray nozzles prior to atomization. Unlike X-rays, for which penetration depth of heavy metals is limited, neutrons are able to penetrate deeply into some metals, including aluminum, lead, and steel. Neutron imaging also complements X-ray imaging in light element detection, especially hydrogen, due to the large incoherent scattering cross section (80 b, in which 1 b = 10^-28 m²) with hydrogen. Thus, for dense near-field liquid sprays, which combine a metal spray nozzle and a hydrogen-based liquid (e.g., hydrocarbon fuels), it is of certain advantage to use neutrons rather than X-rays for imaging measurements. In this work, we conducted proof-of-principle in-situ neutron radiography measurements of metal spray nozzles and water sprays. We compare the neutron imaging results with optical shadowgraph images of the sprays, which show good agreement. Additionally, we demonstrate imaging of the nozzle interior geometry and water inside the nozzle and show that neutron radiography can produce quantitative liquid concentration by two-dimensional snapshot and three-dimensional tomography scans.