High-Speed Flame Radiation Imaging of Thermoacoustic Coupling in a High Pressure Research Thrust Chamber

Kurzfassung

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 which 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 OH* 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 for the oxygen injectors based on hydrodynamic effects is consistent with the contradictory behavior of the two load points.