Session: 04-41 Combustion dynamics - hydrogen flames I

Paper Number: 123877

123877 - Analysis of Thermo-Acoustic Instabilities Induced by Hydrogen Swirling Flames 

A considerable research effort has been focused on combustion dynamics of systems fed with hydrocarbon fuels. The case of pure hydrogen/air flames is less well documented, although such flames are considered in many future applications, most notably in gas turbines and aeroengines. Hydrogen is known for its high reactivity and its tendency to develop thermo-diffusive instabilities. It is thus important to examine hydrogen flame dynamics and investigate the induced combustion instabilities to analyze operational issues that may be encountered in the use of this fuel.

In the present work, self-sustained thermo-acoustic oscillations of pure hydrogen flames are investigated in a swirled jet-in-crossflow configuration already presented in Ref. [1]. The influence of operating conditions on flame stability is investigated through pressure measurements, OH* chemiluminescence and visible light emission imaging. Different types of instabilities are observed. Using Abel-transformed phase-averaged images, it is first shown that the OH* signal originates from the flame reactive layer and that this signal may be used as a reasonable measure of the unsteady heat release rate in the flame. This signal is then used to determine the local Rayleigh source term that feeds acoustic energy in the oscillation. The contributions of this term are then analyzed using a space-time analysis based on an integration of the source term in the transverse direction. This procedure, devised in [2], allows a detailed analysis of the different processes that enhance the acoustic energy in the system, showing, in particular, that a strong positive addition of acoustic energy results from a roll-up of the flame tip and from the quick cyclic reattachment of the flame to the injector tip. A global integration of the Rayleigh source term is then used together with a volume-integrated acoustic energy to estimate the growth rates induced by these driving processes. A reduced order model based on flame transfer function measurements is then employed to calculate growth rates at the various points of operation and compare the estimates obtained in this way with values determined experimentally and with those derived from the limit cycle experiments.   
 

[1] N. Vaysse, D. Durox, R. Vicquelin, S. Candel A. Renaud (2023) Stabilization and dynamics of pure hydrogen swirling flames using cross-flow injection. ASME Turbo Expo 2023, Boston. ASME Paper GT2023-101977.

[2] G. Vignat, E. Lo Schiavo, D. Laera, A. Renaud, L. Gicquel, D. Durox and S.Candel (2021) Proceedings of the Combustion Institute 38, Dynamics of spray and swirling flame under acoustic oscillations : a joint experimental and LES investigation.

Presenting Author: Nicolas Vaysse Laboratoire EM2C

Presenting Author Biography: PhD student at Laboratory EM2C (CNRS and CentraleSupélec, France). Research topics focused on pure hydrogen flames stabilization and thermo-acoustic instabilities with hydrogen flames.

Authors:

Nicolas Vaysse Laboratoire EM2C
Daniel Durox Laboratoire EM2C
Ronan Vicquelin Laboratoire EM2C
Sébastien Candel Laboratoire EM2C
Antoine Renaud Laboratoire EM2C