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<p>This study investigates thermoacoustic instability within a premixed gas turbine combustor, utilizing large eddy simulation (LES), flame describing function (FDF), and a Helmholtz solver. The primary research objectives are to model the heat release rate accurately using LES with thickened flame (TF) and eddy dissipation concept (EDC) combustion models, to examine the FDF phase and gain under longitudinal, transverse, and simultaneous flame excitation, and to determine combustion instability limits via a three-dimensional Helmholtz solver. The FDF is integrated into the Helmholtz solver to identify mode shapes. The method successfully predicts dominant unstable modes and spatial shapes, offering insight into the onset of thermoacoustic instability. The accuracy of the combustion models is assessed by comparing simulation results with experimental data. Key findings reveal that the EDC combustion model reduces calculation error to below 5% compared to test results, despite costing twice as much computationally as the TF model. The FDF amplitude shows peaks at 30, 60, 85, 165, and 175&#xa0;Hz, demonstrating strong acoustic coupling. The first two unstable modes occur at 110&#xa0;Hz and 170&#xa0;Hz, with the 60&#xa0;Hz mode remaining stable. This research demonstrates the model’s ability to capture instability limits in gas turbine combustors. The multi-physics modeling approach, combining CFD simulations with Helmholtz analyses, offers a thorough understanding of combustion instabilities and aids the design of passive control strategies. The novelty of this research lies in the application of simultaneous excitation within CFD simulation and the examination of its effects on thermoacoustic instability.</p>

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Analysis of Thermoacoustic Combustion Instability in a Premixed Combustor Using LES, FDF and Helmholtz Solver Under Longitudinal, Transverse and Simultaneous Excitation

  • 期刊论文

  • 发表日期：

    2025年6月28日

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  • Ehsan Behzad,
  • Reza Ebrahimi

摘要

This study investigates thermoacoustic instability within a premixed gas turbine combustor, utilizing large eddy simulation (LES), flame describing function (FDF), and a Helmholtz solver. The primary research objectives are to model the heat release rate accurately using LES with thickened flame (TF) and eddy dissipation concept (EDC) combustion models, to examine the FDF phase and gain under longitudinal, transverse, and simultaneous flame excitation, and to determine combustion instability limits via a three-dimensional Helmholtz solver. The FDF is integrated into the Helmholtz solver to identify mode shapes. The method successfully predicts dominant unstable modes and spatial shapes, offering insight into the onset of thermoacoustic instability. The accuracy of the combustion models is assessed by comparing simulation results with experimental data. Key findings reveal that the EDC combustion model reduces calculation error to below 5% compared to test results, despite costing twice as much computationally as the TF model. The FDF amplitude shows peaks at 30, 60, 85, 165, and 175 Hz, demonstrating strong acoustic coupling. The first two unstable modes occur at 110 Hz and 170 Hz, with the 60 Hz mode remaining stable. This research demonstrates the model’s ability to capture instability limits in gas turbine combustors. The multi-physics modeling approach, combining CFD simulations with Helmholtz analyses, offers a thorough understanding of combustion instabilities and aids the design of passive control strategies. The novelty of this research lies in the application of simultaneous excitation within CFD simulation and the examination of its effects on thermoacoustic instability.