Numerical Investigation of Noise Generation and Noise Propagation of Coated Turbulent Swirl Flames
Final Report Abstract
The project was initiated to investigate the close interaction between wall and flame in a confined swirl burner, especially the influence of asymmetric placement inside the combustion chamber was to be analyzed. The understanding of the flame-wall interaction is of great importance in terms of flame response and acoustic sound field, since thermoacoustic instabilities occur in real enclosed swirl burner configurations with annular multiple arrangements in axial, radial, and azimuthal directions, with the azimuthal instability often being the most unstable mode. The acoustic instabilities can lead to flow blow-off, flame blow-out and in the most extreme cases, to combustion chamber structural damage due to the strong pressure waves. To better understand this interaction, a systematic numerical analysis of the interaction between swirl burner and confinement was conducted in this project, which was subdivided into four distinct work packages with its own set of objectives. The numerical analysis was based on LES simulations to obtain the main flow field data, which is then used to compute mean and fluctuation values to evaluate the full noise source contribution via solutions of the APE-4 equations. The reference configuration is a confined flame as described by Moeck et al. 2012. The results of the investigations can be summarized as follows: • The reference simulation was successfully validated against the experimental azimuthal velocity profiles. This constitutes a highly accurate numerical reproduction of the experiment by Moeck et al. • Plenum acoustics were found to greatly impact acoustic response, even for unconfined flames. It is therefore recommended that future investigations on unconfined flames should carefully consider the impact of the burner plenum acoustics on their results. • Regarding the conducted free swirl flame configuration, it was found that the main acoustic source is the noise generated by heat release fluctuations at the flame front. • Subsequently, similar investigations were conducted on the symmetrically confined swirl burner. In contrast to the free swirl flame, the confinement led to an increase on the turbulent kinetic energy, and massive recirculation zones. The change also had a substantial effect on the noise field, i.e, the heat release fluctuation term alone is unable to correctly predict the amplitude of the noise emission, but remains in phase. A detailed analysis also requires the noise generated by velocity fluctuations and the momentum source. Then, can an accurate prediction of the amplitude can be achieved. • Asymmetric confinement leads to lower TKE distribution, to an asymmetric flow field, and to lower limit-cycle amplitudes of the thermoacoustic instability. The influence of the asysmmetric confinement on the thermoacoustic instability is therefore significant, and a high sensitivity of combustion noise and combustion instabilities to the burner geometry was identified. Thus, the results of symmetric confined swirl flames cannot be directly transferred to non-symmetric confined flames. To obtain a general understanding of the effect of non-symmetric confinement further detailed investigations on various burner configurations should be performed.
Publications
- “Noise sources of a lean-premixed jet flame,” AIAA Paper 2018-4088, Jun. 2018
K. Pausch, S. Herff, H. Nawroth, C. Paschereit, and W. Schröder
(See online at https://doi.org/10.2514/6.2018-4088) - “Noise sources of lean premixed flames,” Flow, Turbulence and Combustion, vol. 103, Sep. 2019
K. Pausch, S. Herff, F. Zhang, H. Bockhorn, and W. Schröder
(See online at https://doi.org/10.1007/s10494-019-00032-0) - “Impact of burner plenum acoustics on the sound emission of a turbulent lean premixed open flame,” International Journal of Spray and Combustion Dynamics, vol. 12, p. 175 682 772 095 690, Jan. 2020
S. Herff, K. Pausch, H. Nawroth, S. Schlimpert, C. Paschereit, and W. Schröder
(See online at https://doi.org/10.1177/1756827720956906) - “Noise sources of an unconfined and a confined swirl burner,” Journal of Sound and Vibration, vol. 475, p. 115293, Mar. 2020
K. Pausch, S. Herff, and W. Schröder
(See online at https://doi.org/10.1016/j.jsv.2020.115293) - “Analysis of the sound sources of lean premixed methane–air flames,” GAMM-Mitteilungen, Nov. 2021
S. Herff, K. Pausch, M. Meinke, and W. Schröder
(See online at https://doi.org/10.1002/gamm.202200001) - “Les of a turbulent swirl flame using a mesh adaptive level-set method with dynamic load balancing,” Computers & Fluids, vol. 221, p. 104900, 2021
S. Herff, A. Niemöller, M. Meinke, and W. Schröder
(See online at https://doi.org/10.1016/j.compfluid.2021.104900) - “Impact of non-symmetric confinement on the flame dynamics of a lean-premixed swirl flame,” Combustion and Flame, vol. 235, p. 111701, 2022
S. Herff, K. Pausch, S. Loosen, and W. Schröder
(See online at https://doi.org/10.1016/j.combustflame.2021.111701)
