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The authors demonstrate the use of millisecond x-ray phase-contrast imaging for velocity measurement of particle-laden flows in an optically opaque vessel. Taking advantage of particle size polydispersity, this single-particle tracking approach is extremely effective on flows with tracer particles exhibiting a great size distribution ranging from 1μm to hundreds of micrometers, which is impossible for visible-light-based techniques. Furthermore, a tomographic reconstruction was applied to yield the three-dimensional flow velocity field and its particle size dependence with unprecedented sensitivity.

X-ray in-line phase-contrast imaging along with a single-image phase retrieval reconstruction was used to visualize the near-nozzle breakup of optically dense water jets atomized by a high-speed, annular air flow. The influence of the atomizing air on water mass distribution was investigated to reveal the complex air/liquid interactions at various breakup stages. Unlike low-Weber-number jets, the breakup of high-Weber-number jets can occur in the liquid core, which causes sudden decreases in liquid volume fraction.

A numerical study of the spray transfer processes in an electrostatic rotary bell applicator (ESRB) has been conducted utilizing code for a newly developed simulation code. This code consists of three modularized solvers: a fluid flow solver, a spray dynamics solver, and an electrostatic solver. The development of the code consisted of the following steps. First, the flow solver designed for an unsteady three-dimensional Navier-Stokes equation was developed to simulate the shaping airflow with the initial condition and the boundary condition supported by experimental data. Second, the particle trajectory solver, which interacts with the airflow by momentum coupling, was developed to apply the spray transport processes. Finally, the electrostatic solver was developed to calculate the electrostatic field within the two phase flow field. The integrated code created by combining those three solvers was then applied to simulate the paint spray transport processes according to the operating conditions of interest. The numerical results show that the spray shape is very sensitive to changes in the charge to mass ratio. The voltage setting is a dominant operating parameter affecting the numerical transfer efficiency. The voltage range studied was 0 kV to 90 kV. In addition, the transfer efficiency decreases as the shaping airflow rate increases. However, a high shaping airflow rate produces a more uniform distribution of spray mass on the target plane.