A series of tests are conducted to understand the basic features of the coupling mechanism of combustion pressure with the local heat release fluctuation upon the occurrence of low-frequency instability in a hybrid rocket engine. In stable combustion, combustion pressure fluctuates at the frequency of about 20 Hz because of the thermal lag of solid fuel burning. Also, there exist steady spatial distributions of heat release, which are similar to a shear-layer structure. However, when low-frequency instability occurs, the combustion pressure is amplified, and the luminosity starts to fluctuate at a frequency of about 20 Hz. More interestingly, a positive coupling is observed between two fluctuations. The CH* radical luminosity images and proper orthogonal decomposition analysis show the lumped flow structures with time-varying intensity in unstable combustion. A periodic change in the local heat release appears to generate large-scale flow rotations, and the large-scale flow rotations are likely to be associated with the periodic flame extinction at a frequency of about 20 Hz. Also, the flame extinction seems to take a crucial role in the occurrence of low-frequency instability, although it is not clearly understood why the flame extinction occurs in the specific geometric configuration.
Combustion Dynamics in Postchamber of Hybrid Rocket Using
2017
Article (Journal)
English
Hybrid Rocket Combustion Study
NTRS | 1993
|Hybrid rocket combustion study
AIAA | 1993
|Hybrid Rocket Fuel Combustion Study
British Library Conference Proceedings | 1992
|