Session: 04-23: Combustion Dynamics - Numerical Methods I

Paper Number: 78296

78296 - Prediction of Thermoacoustic Instability and Fluid-Structure Interactions for Gas Turbine Combustor 

Gas turbine combustion is predicted to remain popular in the next few decades due to extensive aviation and power industry demand. Stricter environmental regulations will drive the next generation of gas turbine engines to be more compliant, leading to significant emission reduction. Lean combustion associated with Dry Low NOx (DLN) designs is the critical enabler that drastically reduces emissions. However, modern designs are more susceptible to thermo-acoustic instability, a potentially damaging effect originating from a positive feedback loop between acoustic pressure waves and flame heat release within the burner. The associated abrupt rise in pressure oscillation amplitude (i.e., “limit cycle”) can cause significant deformation and vibration of solid structures leading to damages including casing cracks, fatigue failure of turbine blades, and destruction of the entire device. Therefore, predicting thermo-acoustic instability and the associated interaction between fluid flow and solid walls is critical for the overall numerical modeling of gas turbine combustors. A two-way fluid-structure interaction (FSI) can help to provide a more accurate assessment of engine design by evaluating instantaneous mechanical loads and engine life, all of which can contribute to the gas turbine design and certification process. 

This work utilizes the Ansys Fluent® solver for modeling reacting flow and two-way FSI, applied to a laboratory-scale 3D methane/air burner. The burner features a bluff-body stabilized, lean partially premixed flame experiencing strong thermo-acoustic oscillations. In experiments, a thin steel liner is installed around the main combustion chamber, which heavily interacts with the flame and flow field, to produce large amplitude structural deformation. An unsteady RANS approach uses the Shear Stress Transport (SST) turbulence model and a Flamelet Generated Manifold (FGM) combustion model to predict the turbulent reacting flow within the burner. The solver has a built-in Finite Element (FE) structure model, which simultaneously solves the displacement equations and the turbulent reacting flow governing equations. This way, a fully coupled 2-way FSI simulation is carried out to predict thermo-acoustic instabilities in the burner and associated wall deformations. Overall pressure oscillation and liner wall displacement (frequency and amplitude) are in good agreement with experimental data with results for different operating conditions. Although the studied combustor is simplistic, the established 2-way FSI workflow will support commercial gas turbine combustor design and prognosis.

Presenting Author: Yu Xia Ansys UK Ltd.

Presenting Author Biography: Yu Xia is an R&D Engineer at Ansys UK and a Chartered Engineer at Engineering Council, UK. He works on CFD software development and application. He obtained his PhD degree at Imperial College London on Combustion Instability in Gas Turbine Combustors, and has more than 5 years experience on Combustion, Multiphase flow, Heat Transfer, Fluid-Structure Interaction, etc. He has also published several top journal papers and 20+ conference papers on the above topics. More details can be found on his LinkedIn page: linkedin.com/in/steven-xia

Authors:

Yu Xia Ansys UK Ltd.
Ishan Verma Ansys Software Pvt. Ltd.
Alok Khaware Ansys Software Pvt. Ltd.
Patrick Sharkey Ansys UK Ltd.
Davor Cokljat Ansys UK Ltd.