• Journal of the Korean Society of Propulsion Engineers
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• v.10 no.3
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• pp.41-47
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• 2006

Effects of mean flow and nozzle damping on acoustic tuning of a gas-liquid scheme coaxial injector are investigated numerically adopting a linear acoustic analysis. The injector plays a role as a half-wave acoustic resonator for acoustic damping in a combustion chamber of a liquid rocket engine. As Mach number of mean flow in a chamber increases, the resonant frequency of the first tangential mode decreases slightly and the optimum injector tuning length varies negligibly. Nozzle damping affects neither the resonant frequency nor the optimum length. From these numerical results, effects of mean flow and nozzle damping on acoustic tuning of a resonator are negligible. As open area of the injectors increases, the acoustic amplitude decreases, but new injector-coupled modes appear.

• Journal of the Korean Society of Propulsion Engineers
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• v.9 no.4
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• pp.9-15
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• 2005

A linear acoustic analysis is performed to explore the characteristics of acoustic damping by a gas-liquid scheme coaxial injector in a liquid rocket engine. The injector can play a role of acoustic resonator. Acoustic-damping characteristics of half-wave resonator are compared with those of quarter-wave resonator. Various effects of the boundary absorption coefficient, injector length and sound speed in combustion chamber and resonator are investigated. As a result, short tuning length of resonator and low sound speed of the medium have a favorable effect on acoustic damping. As the boundary absorption coefficient decreases, the tuning range of the resonator length becomes narrower.