Abstract
In this work a three-dimensional finite element (FEM) code is
used to perform the stability analysis of an experimental rig designed
and operated in order to study the propensity of full-scale
industrial burners to thermo-acoustic combustion instabilities. The
Burner Transfer Matrix (BTM) approach is used to characterize the
influence of the burner. An experimental transfer matrix is used and
compared with an analytical model. In the combustion chamber,
the influence of the three—dimensional spatial distribution of the
thermodynamics quantities in presence of the flame is considered.
Reynolds Averaged Navier-Stokes (RANS) computational fluid dynamics
(CFD) simulations are used to compute the base flow. A
linear stability analysis of the entire system is performed considering
the coupling between pressure oscillations (p’) and heat release
fluctuations (q’) with a distributed n-t linear Flame Transfer Function
(FTF). A three-dimensional spatial distribution of time delay
(ｔ) is reconstructed assuming the delay due to convection as the
predominant effect. Under these assumptions a good agreement between
numerical and experimental results is found both in terms of
thermo-acoustic resonant frequencies and mode shape of the resonant
modes for different setups of the analyzed system.
