Occurrence of multiple flame fronts in reheat combustors

Gant, Francesco; Scarpato, Alessandro; Bothien, Mirko R.

doi:10.1016/j.combustflame.2019.04.013

Cited by 11 publications

(10 citation statements)

References 27 publications

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“…11 Consequently, the flame position is largely affected and so is the heat release rate fluctuation. 10 It has to be noted that this effect is very distinct for the BFS configuration studied here since the resulting flame is almost only autoignition stabilized. This can be deduced from the almost vertical flame front in Figure 1 and is due to the very low turbulence levels at the inlet.…”

Section: Discussionmentioning

confidence: 77%

“…This discontinuity can be modelled to be at rest or in motion. As was for example shown in a recent publication, 10 in reheat flames the flame front position is highly responsive to the modification of the autoignition delay time of the unburnt mixture. This in turn is influenced by the excitation applied at the system boundary.…”

Section: Introductionmentioning

confidence: 73%

“…The reason for the observed mismatch is that autoignition stabilized flames are characterized by non-negligible oscillations with respect to their mean position even for relatively small fluctuations of the inlet parameters. 10 This is accounted for by the flame velocity fluctuation term u .1em f l ′. When dealing with thermoacoustics of propagation flames this term can be sometimes neglected without affecting the results significantly, 22 but necessarily needs to be included to correctly represent the generation of entropy waves.…”

Section: Discussionmentioning

confidence: 99%

“…Research at Ansaldo Energia of Bothien and co-workers focuses on flame transfer functions and matrices. [8][9][10][11] Schulz and Noiray 12,13 as well as Aditya et al 14 and Gruber et al 15 investigate the occurrence of propagation and autoignition stabilized regimes of reheat flames. In contrast to propagation stabilized flames, only a few studies on analytical modelling approaches for autoignition flame acoustics exist.…”

Section: Introductionmentioning

confidence: 99%

“…Figure 4 this line is significantly differing from the other curves. The reason for the observed mismatch is that autoignition stabilized flames are characterized by non-negligible oscillations with respect to their mean position even for relatively small fluctuations of the inlet parameters 10. This is accounted for by the flame velocity fluctuation term u ′ fl .…”

mentioning

confidence: 99%

See 4 more Smart Citations

Autoignition flame transfer matrix: Analytical model versus large eddy simulations

Gant¹,

Cuquel²,

Bothien

2022

International Journal of Spray and Combustion Dynamics

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Modern gas turbines need to fulfil increasingly stringent emission targets on the one hand and exhibit outstanding operational and fuel flexibility on the other. Ansaldo Energia GT26 and GT36 gas turbine models address these requirements by employing a combustion system in which two lean premixed combustors are arranged in series. Due to the high inlet temperatures from the first stage, the second combustor stage predominantly relies on autoignition for flame stabilization. In this paper, the response of autoignition flames to temperature, pressure and velocity excitations is investigated. The gas turbine combustor geometry is represented by a backward-facing step. Based on the conservation equations an analytical model is derived by solving the linearized Rankine-Hugoniot conditions. This is a commonly used analytical approach to describe the relation of thermodynamic quantities up- and downstream of a propagation stabilized flame. In particular, the linearized Rankine-Hugoniot jump conditions are derived taking into account the presence of a moving discontinuity as well as upstream entropy inhomogeneities. The unsteady heat release rate of the flame is modelled as a linear superposition of flame transfer functions, accounting for velocity, pressure, and entropy disturbances, respectively. This results in a 3[Formula: see text]3 flame transfer matrix relating both primitive acoustic variables and the temperature fluctuations across the flame. The obtained analytical expression is compared to large eddy simulations with excellent agreement. A discussion about the contribution of the single terms to the modelling effort is provided, with a focus on autoignition flames.

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Section: Discussionmentioning

confidence: 77%

Section: Introductionmentioning

confidence: 73%