Measurement of biodiesel blend and conventional diesel spray structure using X-ray radiography

The near-nozzle structure of several non-evaporating biodiesel blend sprays has been studied using x-ray radiography. Radiography allows quantitative measurements of the fuel distribution in sprays to be made with high temporal and spatial resolution. Measurements have been made at different values of injection pressure, ambient density, and with two different nozzle geometries to understand the influences of these parameters on the spray structure of the biodiesel blend. These measurements have been compared to corresponding measurements of Viscor, a diesel calibration fluid, to demonstrate the fuel effects on the spray structure. Generally, the biodiesel blend spray has a similar structure to the spray of Viscor. For the nonhydroground nozzle used in this study, the biodiesel blend spray has a slightly slower penetration into the ambient gas than the Viscor spray. The cone angle of the biodiesel blend spray is generally smaller than that of the Viscor spray, indicating that the biodiesel blend spray is denser than the Viscor spray. For the hydroground nozzle, both fuels produce sprays with initially wide cone angles that transition to narrow sprays during the steady-state portion of the injection event. These variations in cone angle with time are timed later for the biodiesel blend spray than for the Viscor spray, indicating that the dynamics of the injector needle as it opens are somewhat different for the two fuels.