Abstract
We study the formation mechanism of high-frequency combustion oscillations in a model rocket combustor from the viewpoints of symbolic dynamics and complex networks. The flow velocity fluctuations in the fuel injector generated by the pressure fluctuations in the combustor give rise to the periodic ignition of the unburnt fuel/oxidizer mixture, resulting in a significant change in the heat release rate fluctuations in the combustor. The heat release rate fluctuations drive the pressure fluctuations in the combustor before a transition state, while the pressure fluctuations in the combustor gradually begin to significantly affect the heat release rate fluctuations during the transition to combustion oscillations. The directional feedback process during the transition and subsequent combustion oscillations is identified by the directionality index of the symbolic transfer entropy. The thermoacoustic power network enables us to understand the physical mechanism behind the transition and subsequent combustion oscillations.
Highlights
Combustion oscillations are manifested as organized combustion oscillations with large-amplitude and high-frequency and arise from the strong mutual interaction between unsteady heat release rate and acoustic pressure fluctuations in a combustor
The flow velocity fluctuations in the fuel injector generated by the pressure fluctuations in the combustor give rise to the periodic ignition of the unburnt fuel/oxidizer mixture, resulting in a significant change in the heat release rate fluctuations in the combustor
We have clarified the formation mechanism of high-frequency combustion oscillations in a model rocket combustor using sophisticated analytical methods based on symbolic dynamics and complex networks
Summary
Combustion oscillations are manifested as organized combustion oscillations with large-amplitude and high-frequency and arise from the strong mutual interaction between unsteady heat release rate and acoustic pressure fluctuations in a combustor. Murugesan and Sujith studied the dynamic behavior of combustion noise and combustion oscillations in a bluff-body-type turbulent combustor using the visibility graph.. Murugesan and Sujith studied the dynamic behavior of combustion noise and combustion oscillations in a bluff-body-type turbulent combustor using the visibility graph.15 They showed that a scale-free structure related to fractality appears in the degree distribution in the graph during combustion noise, while the scale-free structure collapses during combustion oscillations. Okuno et al. reported the possible presence of highdimensionality and small-world-like nature in the pressure fluctuations during combustion oscillations in a swirl-stabilized turbulent combustor using cycle networks and phase space networks.. Mondal et al. studied the synchronized state between the pressure
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