액체 로켓엔진 분사기의 음향감쇠 효과에 관한 수치적 연구

Abstract

In combustion chamber of liquid rocket engine, acoustic fine tuning of gas-liquid scheme injector is studied numerically for acoustic stability by adopting linear acoustic analysis. Acoustic behavior in the combustor with a single injector is investigated and acoustic-damping effect of the injector is evaluated for cold condition by the quantitative parameter of damping factor as a function of injector length. From the numerical results, it has been found that the injector can play a significant role in acoustic damping. Optimum injector length corresponds to a half of a full wavelength of the first longitudinal mode traveling in the injector with the acoustic frequency intended for damping in the chamber. In the baffled chamber, the optimum lengths of the injector are calculated as a function of baffle length for both cold and hot conditions. Next, in the combustor with numerous injectors, peculiar acoustic coupling between combustion chamber and injectors has been observed. As the injector length approaches a half wavelength, the new injector-coupled acoustic modes occur and thereby, the acoustic-damping effect of the tuned injectors is appreciably degraded.