Core Length and Spray Width Measurements in Shear Coaxial Rocket Injectors from X-ray Radiography Measurements.

摘要

Shear coaxial injectors are so named because they rely on the shear between an outer low-density, high-velocity annulus and a high-density, low-velocity inner jet to atomize and mix a liquid and a gas. These sprays have an intact core near the injector and the high amount of light scattering its corrugated surface produces creates large optical densities. These high optical densities, in turn, make interrogation of the spray field in the intact core difficult. In combustion applications, such as rockets, this region is also the area of flame holding, and so is of primary importance in predicting combustion behavior. To overcome the problems of multiple scattering, the near-injector region was studied using x-ray radiography at Argonne National Laboratory's Advanced Photon Source. These results clearly show regions which correspond to changes in atomization behavior and can be used to quantify "core length" and understand more clearly what this term means. Three methods are explored to measure core length from x-ray radiography data and are compared to two-phase core length measurements from the literature. The core length nondimensionalized by the inner jet diameter was found to scale with the momentum flux to the -0.66 power.