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Communication Dans Un Congrès Année : 2022

Low-order models for acoustic modes in a ramjet combustor with inlet shock train

Résumé

The acoustic field inside a model ramjet combustor featuring a low frequency combustion instability is investigated with a set of low-order models of increasing complexity. Under the conditions investigated, the ramjet features a shocked flow at the combustion chamber nozzle outlet and a shock train at its air inlets characterized by a displacement synchronized with the combustion oscillation. The objective is to understand by which acoustic boundary condition the moving shock train can be replaced to model the downstream acoustic field. Four analytical models are tested and compared to POD results from LES data. Models 1 and 2 consider a fixed shock that respectively behaves as a pressure node and a velocity node. Model 3 includes the displacement of the shock due to pressure disturbances inside the combustion chamber. Finally, model 4 also takes into account effects of the mean flow velocity on the acoustic field. From these comparisons, it is concluded that a moving velocity node reproduces a better shape of the mode in the vicinity of the shock train than a pressure release. Moreover, model 4 that includes mean flow effects yields a similar frequency and a similar mode shape in the vicinity of the shock train as in the data from numerical simulations. However, a closer comparison with these data shows that the model fails to reproduce the deformation and the magnitude of displacement of the mode and suggests that a more complex dynamics needs to be considered.
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Dates et versions

hal-03773873 , version 1 (09-09-2022)

Identifiants

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Erwin Bekaert, Aurélien Genot, Thomas Le Pichon, Thierry Schuller. Low-order models for acoustic modes in a ramjet combustor with inlet shock train. EUCASS-3AF 2022, Jun 2022, Lille, France. ⟨10.13009/EUCASS2022-6122⟩. ⟨hal-03773873⟩
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