X-ray Radiography Measurements of Shear Coaxial Rocket Injectors

Shear coaxial injectors are a common injector type for liquid-rocket-propulsion applications and can be found in many oxygen/hydrogen engines. These injectors rely on the shear between an outer lower-density, high-velocity annulus and a higher-density, low-velocity inner jet to atomize and mix the propellants. Because of the dense-jet core, the optical densities of these sprays are high, particularly near the injector where primary atomization and flame holding take place. The large optical density has prevented interrogation, detailed study, and understanding of this important region. The evolution of x-ray radiography techniques using intense x-ray sources (such as Argonne National Laboratory’s Advanced Photon Source) has allowed the measurement of quantitative equivalent path lengths and projected densities in the near-injector regions of shear coaxial injectors. Using water and gaseous nitrogen as propellant simulants at atmospheric backpressure, the effect of momentum flux ratio and mass flux ratio, are investigated for three injector geometries operating at momentum flux ratios spanning the range from 0.5 to 15. Corresponding author: [email protected] Distribution A: Approved for public release; distribution unlimited. Clearance #