Characterization of coaxial rocket injector sprays under high pressure environments

The effect of elevated environment pressures on the atomization characteristics of a single element, scaled-down, shear-coaxial rocket injector has been investigated. In this study, the shear coaxial injector was operated with water and air as simulants for conventionally used liquid oxygen and hydrogen gas, respectively. The experiments were conducted in a specially designed high pressure rig. A two-component PDPA/DSA system was used to study the spray characteristics at different chamber pressures ranging from atmospheric to 100 psig. The study showed an overall increase in the droplet sizes at higher chamber pressures. This phenomenon is attributed to a decrease in the secondary atomization effects at higher chamber pressures which, in turn, is directly related to a decrease in the shear experienced by the droplets as they move axially through the pressure chamber.