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16-04-15 14:15 Age: 3 years

By:  Outi Tammisola (University of Nottingham)

Adjoint-based sensitivity analysis and optimal passive control of hydrodynamic instability in fuel injectors

Achtung: Vortrag findet am Donnerstag statt!

Raum MB 13


Large-scale hydrodynamic oscillations in gas turbine fuel injectors help to mix the fuel and air but can also contribute to thermoacoustic instability. Small changes to some parts of a fuel injector greatly affect the frequency and amplitude of these hydrodynamic oscillations, and parametric studies at high Reynolds numbers are very time-consuming.

We first characterize the large-scale oscillations in a gas turbine's single stream radial swirler, which has been extensively studied experimentally. This is done by extracting POD modes from DNS, and by computing the linear global modes around the DNS mean flow. Next, we identify the wavemaker (most influential region for generic control of the instability) by adjoint-based sensitivity analysis. The wavemaker is found to be inside the nozzle, underlying the importance of nozzle design. We find that including the eddy viscosity in the linear global stability analysis significantly improves the quantitative agreement between linear global modes and POD modes, even though the qualitative behavior is unaffected.

In the final part of the presentation, we will briefly touch upon a new development in adjoint-based sensitivity analysis - second-order perturbations, and how they can help to understand and optimise the effect of controls breaking two-dimensionality of a flow. For example, inflow asymmetry might influence hydrodynamic instability in a two-dimensional fuel injector, and such effect could be predicted and optimised.


16-04-15 14:15 Age: 3 years

By:  Outi Tammisola (University of Nottingham)

Adjoint-based sensitivity analysis and optimal passive control of hydrodynamic instability in fuel injectors

Achtung: Vortrag findet am Donnerstag statt!

Raum MB 13


Large-scale hydrodynamic oscillations in gas turbine fuel injectors help to mix the fuel and air but can also contribute to thermoacoustic instability. Small changes to some parts of a fuel injector greatly affect the frequency and amplitude of these hydrodynamic oscillations, and parametric studies at high Reynolds numbers are very time-consuming.

We first characterize the large-scale oscillations in a gas turbine's single stream radial swirler, which has been extensively studied experimentally. This is done by extracting POD modes from DNS, and by computing the linear global modes around the DNS mean flow. Next, we identify the wavemaker (most influential region for generic control of the instability) by adjoint-based sensitivity analysis. The wavemaker is found to be inside the nozzle, underlying the importance of nozzle design. We find that including the eddy viscosity in the linear global stability analysis significantly improves the quantitative agreement between linear global modes and POD modes, even though the qualitative behavior is unaffected.

In the final part of the presentation, we will briefly touch upon a new development in adjoint-based sensitivity analysis - second-order perturbations, and how they can help to understand and optimise the effect of controls breaking two-dimensionality of a flow. For example, inflow asymmetry might influence hydrodynamic instability in a two-dimensional fuel injector, and such effect could be predicted and optimised.


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