Design for Thermo-Acoustic Stability: Procedure and Data Base

Abstract

A Design for Thermo-Acoustic Stability (DeTAS) procedure is presented, that aims at selecting a most stable burner geometry for a given combustor. It is based on the premise that a thermo-acoustic stability model of the combustor can be formulated and that a burner design exists, which has geometric design parameters that sufficiently influence the dynamics of the flame. Describing the burner and flame dynamics in dependence of the geometrical parameters an optimization procedure involving a linear stability model of the target combustor maximizes the damping and thereby yields the optimal geometrical parameters. To demonstrate the procedure on an existing annular combustor a generic burner design was developed that features two geometrical parameters that can easily be adjusted. To provide the data base for the DeTAS procedure static and dynamical properties of burner and flame were measured for three by three configurations at a fixed operation point. The data is presented and discussed. It is found that the chosen design exhibits a significant variability of the flame dynamics in dependence of the geometrical parameters indicating that a DeTAS should be possible for the targeted annular combustor.

Design for Thermo-Acoustic Stability: Modeling of Burner and Flame Dynamics

“…This is in accordance with the observed flame shapes [13], which are flat and compact for the R h ¼ 50% and 100% swirler and, therefore, do not have a significant time delay distribution. The parameters r 2 and r 3 account for the distribution of time delays over the flame.…”

“…As was noted in the companion paper the influence of the head air ratio R h on the burner acoustics is very small [13], so one set of parameters represents all burner acoustics. So except for this L À f element at the burner exit, all elements are without loss.…”

“…The parameters r 2 and r 3 account for the distribution of time delays over the flame. (5) are demonstrated on the comparison between experimental (FTF exp , squares) and modeled [13] (FTF mod , red line) FTF of the R h ¼ 100%, L m ¼ 1.875 d b case. This is in accordance with the observed flame shapes [13], which are flat and compact for the R h ¼ 50% and 100% swirler and, therefore, do not have a significant time delay distribution.…”

“…As discussed in the companion paper [13], a switching behavior of the flame shape with head air ratio precludes an interpolation in the R h dimension. However, the linear dependence of the model parameters on L m þ x OH,max and mixing tube conicity as seen in Fig.…”

“…(1) The first publication [13] that outlines the procedure and discusses the experimental dynamics database, thus proving that a considerable variation of flame dynamics can be obtained for the same operation point with moderate geometry variations. (2) This second paper that provides the modeling of these dynamics and validates the chosen functionals establishes the basis for the optimization.…”