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 radiography was used to measure the behavior of four fuel sprays from a light-duty common-rail diesel injector. The sprays were at 250bar injection pressure and 1bar ambient pressure. Injection durations of 400μs and 1000μs were tested, as were axial single-hole nozzles with hydroground and nonhydroground geometries. The X-ray data provide quantitative measurements of the internal mass distribution of the spray, including near the injector orifice. Such measurements are not possible with optical diagnostics. The 400μs sprays from the hydroground and nonhydroground nozzles appear qualitatively similar. The 1000μs spray from the nonhydroground nozzle has a relatively consistent moderate width, while that from the hydroground nozzle is quite wide before transitioning into a narrow jet. The positions of the leading- and trailing-edges of the spray have also been determined, as has the amount of fuel residing in a concentrated structure near the leading edge of the spray.