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

Abstract

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.