LIQUID ROCKET COMBUSTION CHAMBER-CHARACTERIZATION OF THEACOUSTIC BEHAVIOR TO AVOID COMBUSTION INSTABILITIES

摘要

Over the last 40 years, many solid and liquid rocket motors have experienced combustioninstability. Combustion instability is the interaction of the inherent oscillatory acoustic modeswith the combustion and/or fluid dynamic processes inside the combustion chamber. Studieshave been showing that, even if less than one percent of the available energy is diverted to anacoustic mode, combustion instability can already be generated.On one hand, this instability can lead to ballistic pressure changes, couple with other motorcomponents such as guidance or thrust vector control, and in the worst case, cause motorstructural failure. In this case, measures, applying acoustic techniques, must be taken tocorrect/minimize these influences on the combustion. On the other hand, combustioninstability, although present, does not cause system problems and can be tolerated. In thiscase, it still must be characterized and understood.This paper describes the applied procedures to characterize the acoustic behavior in the innercavity of four different configurations of a combustion chamber. The simple analyticalmodels are generated and the calculated acoustic resonances are compared with the measuredacoustic natural frequencies, using cold flow inside the chamber cavity. Some commentsabout the measurement procedures are done, as well as the next steps for the continuity ofthis research.