Development of Nonuniformities in Swirling, Rocket Injectors
AIR FORCE RESEARCH LAB EDWARDS AFB CA PROPULSION DIR
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A high-performing, stable rocket engine requires injectors which produce predictable, uniform, temporally stable sprays. The use of high-velocity gas to atomize a liquid, such as in an ox-rich engine cycle, can produce complex, unsteady behavior. Two types of unsteady behavior, pulsing and changes in the spray s centerline, were observed in a specific type of prefilming rocket injector a Gas-Centered Swirl Coaxial GCSC injector. The reason for this unsteadiness is not well understood, and developing an improved understanding is complicated by the high optical density of the spray and its axisymmetric, swirling nature. Recent advances in image processing techniques through the use of Proper Orthogonal Decomposition POD and in time-resolved x-ray diagnostics are enabling additional information to be extracted from the spray and improving the understanding of spray instabilities. Here a series of geometries and operating conditions of GCSC injectors are examined with traditional image processing techniques to elucidate the basic nonuniform behavior of the spray and atomizing film. A single test condition is examined in detail using POD and time-resolved x-ray radiography. The results of these two techniques compare favorably with the traditional processing and complement the traditional approach by providing additional information. The POD analysis allows visualization of the location of unsteady structures, and the radiography provides details of the spray changes i.e. changes in droplet size during the unsteadiness.
- Operations Research
- Rocket Engines