Investigation of Combustion Control in a Dump Combustor Using the Feedback Free Fluidic Oscillator

A feedback free fluidic oscillator was designed and integrated into a single element rocket combustor withthe goal of suppressing longitudinal combustion instabilities. The fluidic oscillator uses internal fluid dynamicsto create an unsteady outlet jet at a specific frequency. An array of nine fluidic oscillators was tested to mimicmodulated secondary oxidizer injection into the combustor dump plane. The combustor has a coaxial injectorthat uses gaseous methane and decomposed hydrogen peroxide with an overall O/F ratio of 11.7. A sonicchoke plate on an actuator arm allows for continuous adjustment of the oxidizer post acoustics enabling thestudy of a variety of instability magnitudes. The fluidic oscillator unsteady outlet jet performance is comparedagainst equivalent steady jet injection and a baseline design with no secondary oxidizer injection. At themost unstable operating conditions, the unsteady outlet jet saw a 67% reduction in the instability pressureoscillation magnitude when compared to the steady jet and baseline data. Additionally, computational fluiddynamics analysis of the combustor gives insight into the flow field interaction of the fluidic oscillators. Theresults indicate that open loop high frequency propellant modulation for combustion control can be achievedthrough fluidic devices that require no moving parts or electrical power to operate.