Nozzle Geometry and Injection Duration Effects on Diesel Sprays Measured by X-Ray Radiography

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.