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Communication Dans Un Congrès Année : 2015

Issues, progress and challenges in combustion dynamics

Résumé

The dynamics of annular combustors is of considerable interest because this geometry is used in practical systems of importance like jet engines and gas turbines. In general, these combustors are equipped with multiple injectors. This situation features various complexities which are being investigated by making use of novel experimental devices, new low order models and comprehensive large eddy simulations. This review is focused on a set of recent studies carried out on laboratory scale combustors allowing detailed studies of dynamical interactions. The ignition transient is considered first by examining experiments carried out in a system comprising a plenum feeding premixed gaseous reactants through multiple swirling injectors and an annular combustor formed by two concentric transparent quartz walls allowing full visualizations of the flame. The analysis focuses on the ``light-round'' process which intervenes at the start ensuring flame spreading from one injector to the next and eventually leading to established flames on each injector. Detailed calculations relying on large eddy simulation complement experiments and retrieve the essential features identified in the experimental analysis. This indicates that considerable progress has been made but it also raises new questions that need further analysis. The second issue to be considered is that of combustion instabilities coupled by azimuthal modes. These dynamical phenomena are important because they degrade the operation of the system and may have serious consequences. The underlying coupling phenomenon is often observed in the advanced premixed combustion systems used in modern gas turbines. High-speed imaging allows a detailed examination of the flame dynamics in combination with pressure measurements recorded in the chamber or in the plenum. Different types of injectors have been studied including swirling units and matrix devices with multipoint injection channels. In the case of swirling injectors, it is found that the coupling continuously evolves between standing and spinning modes and that this can be characterized by determining a spin ratio. In the configuration comprising matrix injectors combustion takes place through a set of conical flames stabilized on perforated plates allowing an interesting simplification of the combustion process. This gives rise to various couplings including spinning modes, purely standing modes and situations where two different modes sustain oscillations. These various cases will be examined and their analysis may be carried out with dynamical models making use of the flame describing function of individual injectors.
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Dates et versions

hal-01345640 , version 1 (14-07-2016)

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  • HAL Id : hal-01345640 , version 1

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S. Candel, D. Durox, Thierry Schuller. Issues, progress and challenges in combustion dynamics: Invited plenary lecture. 10th Asian Pacific Combustion Conference, Chinese section of the Combustion Institute, Jul 2015, Beijing, China. ⟨hal-01345640⟩
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