Impact of fuel supply impedance and fuel staging on gas turbine ...

Numerical analysis <strong>of</strong> thermo-acoustic instabilities
ideally also account for the dispersion due to the turbulent flow field in the
mixing section <strong>and</strong> swirler.
In the present work jet-in-cross flow injectors are used. In consideration <strong>of</strong>
the modeling uncertainties associated with cases B, C <strong>and</strong> D, case A is chosen,
which has the advantage <strong>of</strong> a straightforward <strong>and</strong> exact implementation.
Therefore the mixing section, a part <strong>of</strong> the injection tubes, the swirler <strong>and</strong> the
combustion chamber are simulated in the following. The velocity fluctuations
at the location <strong>of</strong> injection <strong>and</strong> at the burner exit, which can be directly coupled
to the corresponding flame element in the network model, are used as
input signals for the identification routine. Except the acoustic characteristics
<strong>of</strong> the swirler, which will be also determined using CFD/SI, the acoustic network
elements representing all other parts <strong>of</strong> the combustion system can be
derived analytically. The acoustic network model obtained can then be used
to analyze the acoustic behavior <strong>of</strong> practical premixed combustion systems
using multiple, staged <strong>fuel</strong> injectors with tuned <strong>impedance</strong>s.
The next chapters describe the theory <strong>and</strong> the models, which are required for
the present purpose. Chapter 3 describes the basic acoustic relations <strong>of</strong> the
network model. The introduction <strong>of</strong> Computational Fluid Dynamics with the
chosen numerical turbulence <strong>and</strong> combustion models is discussed in chapter
4. The system identification method with its extension to determine multipleinput
single-output systems is addressed in chapter 5.
42