Development of a Non-premixed GOx/Methane Resonance Igniter

Resonance igniters are a promising alternative to conventional ignition devices for rocket engines using non-hypergolic propellants. This paper presents the development and analysis of a resonance igniter using gaseous oxygen and methane, supported by experimental measurements and numerical modelling. The effect of nozzle gap distance on acoustic resonance heating is investigated using oxygen and nitrogen as driving gases. Microphone data are used to determine the operating mode of the igniter; thermocouple data acquired on the outside of the resonator tip are used to evaluate heating performance across various nozzle pressure ratios and nozzle gap distances. A numerical model based on the open-source CFD software SU2 is developed and validated against resonance heating experimental data. This non-reacting flow model accurately captures the transition from the high-frequency Jet Screech Mode to the lower-frequency Jet Regurgitant Mode. Furthermore, it identifies the operational parameters leading to the highest rates of resonance heating observed in the experiments. Ignition attempts in non-premixed conditions, using gaseous oxygen and methane, show that the separate injection of methane in cross-flow into the combustion chamber causes severe disruption of resonance heating, preventing ignition. • A resonance igniter using gaseous oxygen (GOx) and methane was designed and tested for rocket propulsion applications. The igniter operates by coupling a supersonic gas jet with an acoustic cavity to generate localized heating without electrical components. • The thermoacoustic heating performance was characterized across a range of nozzle pressure ratios and nozzle-resonator gaps. The experimental results demonstrate two distinct acoustic modes, jet screech mode (JSM) and jet regurgitant mode (JRM), including the transition between them. • A compressible CFD model developed in SU2 successfully predicts the dominant acoustic frequencies and mode transitions. • This study highlights key limitations of non-premixed operation in thermoacoustic igniters with gaseous fuels. The mixing of the fuel with the oxidizer disrupts the resonant heating, preventing successful ignition. • Findings support the design of non-hypergolic, green ignition systems for space propulsion using alternative propellants.