Session: 04-09 Combustion Dynamics III

Submission Number: 175443

Large Eddy Simulations of Piloted, Swirl-Stabilized Flames: Instabilities Under Varying Combustor Lengths 

Understanding and predicting thermoacoustic instabilities in lean premixed industrial gas turbine combustors remain essential for ensuring operability, reliability, and smooth performance. Previous experimental studies on the Solar Turbines' Taurus 70 SoLoNox system have shown that combustor geometry, particularly the effective combustor length, strongly modulates the flame acoustic coupling and can give rise to distinct instability modes. In this work, Large Eddy Simulations (LES) are performed to investigate the influence of combustor length on the stability characteristics of a swirl-stabilized, piloted premixed flame operating under atmospheric conditions. The computational configuration replicates a single injector variable-length combustor, enabling systematic assessment of four representative lengths spanning stable and unstable regimes observed experimentally. A fully compressible, GPU resident LES solver coupled with a premixed flamelet progress variable (FPV) model is employed. Simulation results demonstrate good agreement with test rig measurements in terms of the dominant oscillation frequency and the qualitative thermoacoustic response.
Power spectrum density (PSD) analysis reveals that the LES accurately captures the experimentally observed acoustic mode structure, with unstable configurations exhibiting sharply defined peaks characteristic of self excited thermoacoustic oscillations. Dynamic Mode Decomposition (DMD) further identifies a pronounced push-pull oscillation pattern that governs the instability dynamics, and highlights the role of geometric constrictions and localized quenching of hot gases in establishing acoustic isolation within the combustor. While discrepancies in predicted mode amplitude occur for one intermediate configuration, the overall agreement underscores the capability of high fidelity LES to resolve both global and localized features of flame acoustic coupling in practical combustors at various lengths. The findings provide new insight into how combustor length influences mode selection and heat release dynamics, and highlight the importance of accurate thermal boundary representations in predicting thermoacoustic behavior in lean premixed gas turbine systems.

Presenting Author: Islam Kabil Argonne National Laboratory

Presenting Author Biography: Islam Kabil is a Postdoctoral Scholar at Argonne National Laboratory, where he works in the Multi-Physics Computations group. He earned his Ph.D. in Mechanical Engineering from the University of Connecticut in 2024, where his research focused on plasma-assisted ignition, chemical kinetic mechanism reduction, and combustion modeling. His current work at Argonne centers on high-fidelity and reduced-order modeling of turbulent combustion in industrial gas turbine combustors, with a focus on understanding and mitigating combustion instabilities

Authors:

Islam Kabil Argonne National Laboratory
Yonduck Sung Solar Turbines Incorporated
Daniel Johnson Solar Turbines Incorporated
James Blust Solar Turbines Incorporated
Lee Shunn Cadence Design Systems
Jonathan Wang Cadence Design Systems
Chao Xu Argonne National laboratory