Flame Transfer Function for Swirled LPP Combustion From Experiments and CFD

Abstract

Combustion oscillations that arise in gas turbines can lead to plant damage. One method used to predict these oscillations is to analyse the acoustics using a simple linear model. This model requires a transfer function to describe the response of the heat release to flow perturbations. A transfer function has been obtained for a swirled premixed combustion system using experiments under atmospheric conditions and CFD. These results have been compared with analytical models.The experimental and computational transfer functions both indicate a low frequency zero. A time-delay spread model gives a good representation of the computational transfer function. The experimental transfer function is described well by a model that combines a time-delay spread with a constant gain.

Simulation of the flame describing function of a turbulent premixed flame using an open-source LES solver

“…The linear FTF of several flames has been extracted using URANS (Unsteady Reynolds-Averaged Navier-Stokes) simulations, giving reasonable results [27,28,29]. Armitage et al [7] used URANS to obtain the FDF for the bluff body stabilised premixed flame experimentally investigated by Balachandran et al [5], capturing qualitatively the shape of the response, but with a significant offset in the amplitude of the heat release rate fluctuations.…”

Investigation of the nonlinear response of turbulent premixed flames to imposed inlet velocity oscillations

“…Transfer functions may be obtained from experiments (e.g., Bloxsidge et al [5], Kulsheimer and Buchner [6]), from steady (Armitage et al [7], Flohr and Paschereit [8]) or unsteady (Zhu et al [9], Armitage et al [10], Gentemann et al [11]) CFD, or from flame models (Dowling [12], Sattelmayer [13], Cho and Lieuwen [14]) that try to represent the flame behavior by simple analytical descriptions.…”

Prediction of limit cycle oscillations in gas turbine combustion systems using the Flame Describing Function

“…Dowling et al [4,26] derived that the equivalence ratio fluctuations can be related to the velocity fluctuations at the location of fuel injection as:…”

“…* The FTF can be obtained by experimental methods [47,48,62], analytical methods (such as the n − τ time lag model [16,17] or Dowling's kinematic flame model [25]), as well as from Computational Fluid Dynamics (see e.g. Armitage et al [4], van Kampen [47] or Polifke [12,76]). In the state of the art CFD procedure, the FTF is determined by Large Eddy Simulations where the flame is excited by perturbing the boundaries of the combustor using a broadband frequency signal [12].…”

“…Armitage et al [4], van Kampen [47] and Polifke et al [12,76]. In this work, the procedure will be extended to Flame Describing Functions.…”