Injector-Driven Flame Dynamics in a High-Pressure Multi-Element Oxygen–Hydrogen Rocket Thrust Chamber

This work addresses the nature of supercritical hydrogen-oxygen flame coupling to acoustics through visualization under conditions representative of upper-stage rocket engines. A research thrust chamber that shows self-excited combustion instabilities for certain operating conditions was used. Previous analysis proved that the instabilities are connected to injector acoustics. In this study a small optical access window was mounted in the chamber wall. High-speed flame radiation imaging of UV and blue wavelengths has been applied in order to analyze the acoustic-flame interaction of one of the 42 flames. Dynamic mode decomposition results for a case with 80-bar chamber pressure showed that the flame dynamics are strongly influenced by the LOX injector acoustics, whereas for a 50-bar chamber pressure load point no flame response to injector acoustics was observed. A potential source of acoustic excitation in the oxygen injectors based on hydrodynamic effects is consistent with the observations from the two load points.