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International Journal of Energetic Materials and Chemical Propulsion
ESCI SJR: 0.142 SNIP: 0.16 CiteScore™: 0.29

ISSN Print: 2150-766X
ISSN Online: 2150-7678

International Journal of Energetic Materials and Chemical Propulsion

DOI: 10.1615/IntJEnergeticMaterialsChemProp.v3.i1-6.380
pages 365-378

REAL-TIME X-RAY RADIOGRAPHY STUDY OF LIQUID JET BREAKUP FROM ROCKET ENGINE COAXIAL INJECTORS

R. D. Woodward
Propulsion Engineering Research Center and Department of Mechanical Engineering, The Pennsylvania State University University Park, PA 16802
R. L. Burch
Propulsion Engineering Research Center and Department of Mechanical Engineering, The Pennsylvania State University University Park, PA 16802
Fan-Bill Cheung
Department of Mechanical & Nuclear Engineering, Pennsylvania State University, University Park, PA 16802

ABSTRACT

The investigation of liquid jet breakup and spray development is critical to the understanding of combustion phenomena in liquid-propellant rocket engines. A great deal of work has been done to characterize low-speed liquid jet breakup and dilute sprays, but atomizing jets and dense sprays have yielded few quantitative measurements due to their optical opacity. The present work focuses on a characteristic of the primary breakup process of round liquid jets, namely the length of the intact liquid core. The specific application considered is that of shear-coaxial-type rocket engine injectors. Real-time x-ray radiography, capable of imaging through the dense two-phase region surrounding the liquid core, is used to make the measurements. The intact liquid-core length data have been obtained and interpreted to illustrate the effects of chamber pressure (gas density), injected-gas and liquid velocities, and cavitation. The results show clearly that the effect of cavitation must be considered at low chamber pressures since it can be the dominant breakup mechanism. A correlation of intact core length in terms of gas-to-liquid density ratio, liquid jet Reynolds number, and Weber number is suggested. The gas-to-liquid density ratio appears to be the key parameter for aerodynamic shear breakup in this study.