Modelling Flame-Generated Noise in a Partially Premixed, Bluff Body Stabilized Model Combustor

Abstract

Numerical simulation using Computational Fluid Dynamics (CFD) has become increasingly important as a tool to predict the potential occurrence of combustion instabilities in gas turbine combustors operating in lean premixed mode. Within the EU-funded Marie Curie project, LIMOUSINE (Limit cycles of thermo-acoustic oscillations in gas turbine combustors), a model test burner has been built in order to have reproducible experimental results for model validation. The burner consists of a Rijke tube of rectangular section having a flame-stabilizing wedge at about 1/4 of its length. Fuel and air supplies were carefully designed to give closed end acoustic inlet boundary conditions while the atmospheric outlet representing an acoustically open end. A transient CFD simulation of the turbulent, partially premixed, bluff body stabilized combusting flow has been carried out for the LIMOUSINE burner using ANSYS CFX commercial software. A 2-D section has been modelled by means of the scale resolving turbulence model, Scale-Adaptive Simulation (SAS), and a two-step Eddy Dissipation combustion model. Experiments were performed on the LIMOUSINE model burner to measure the dynamic variation of pressure and temperature. Results were obtained for several cases with power input ranging from 40 to 60 kW and air factors between 1.2 and 1.8. The CFD results are found to be in good agreement with experiments: the flame is predicted to stabilise on the bluff body in the fluid recirculation zone; resonance frequencies are found to change depending on power and air excess ratio and have a good agreement with experimental results and analytical values; pressure oscillations are consistent with pipe acoustic modes.

Sensitivity of Combustion Driven Structural Dynamics and Damage to Thermo-Acoustic Instability: Combustion-Acoustics-Vibration

“…A considerable amount of work has been published in the combustion research area in terms of fluid dynamics, improvement of efficiency, and emissions [3][4][5][6][7][8]. Furthermore, together with the published research on the thermo-acoustic instabilities in the literature [1,[9][10][11][12][13][14], the coupled-domains within the thermo-acoustic feedback mechanism have been investigated to include the multiphysics such as combustion-acoustics [15,16] and acoustics-vibrations [17,18]. instabilities analysis to cover the two-way interaction of the fluidstructure [22][23][24], however, the results are not linked to structural damage conditions.…”