scholarly journals Prediction of combustion instability limit cycle oscillations by combining flame describing function simulations with a thermoacoustic network model

2015 ◽  
Vol 162 (10) ◽  
pp. 3632-3647 ◽  
Author(s):  
Xingsi Han ◽  
Jingxuan Li ◽  
Aimee S. Morgans
Keyword(s):  
Limit Cycle ◽  
Network Model ◽  
Combustion Instability ◽  
Limit Cycle Oscillations ◽  
Describing Function ◽  
Flame Describing Function

Describing Function Analysis of Limit Cycles in a Multiple Flame Combustor

2011 ◽  
Vol 133 (6) ◽  
Author(s):  
Frédéric Boudy ◽  
Daniel Durox ◽  
Thierry Schuller ◽  
Grunde Jomaas ◽  
Sébastien Candel
Keyword(s):  
Transfer Function ◽  
Limit Cycle ◽  
Limit Cycles ◽  
Function Analysis ◽  
Combustion Instabilities ◽  
Describing Function ◽  
Variable Size ◽  
Theoretical Predictions ◽  
Flame Describing Function ◽  
Oscillation Frequencies

A recently developed nonlinear flame describing function (FDF) is used to analyze combustion instabilities in a system where the feeding manifold has a variable size and where the flame is confined by quartz tubes of variable length. Self-sustained combustion oscillations are observed when the geometry is changed. The regimes of oscillation are characterized at the limit cycle and also during the onset of oscillations. The theoretical predictions of the oscillation frequencies and levels are obtained using the FDF. This generalizes the concept of flame transfer function by including dependence on the frequency and level of oscillation. Predictions are compared with experimental results for two different lengths of the confinement tube. These results are, in turn, used to predict most of the experimentally observed phenomena and in particular, the correct oscillation levels and frequencies at limit cycles.

Effects of Nonlinear Modal Interactions on the Thermoacoustic Stability of Annular Combustors

2018 ◽  
Vol 141 (2) ◽  
Author(s):  
Alessandro Orchini ◽  
Georg A. Mensah ◽  
Jonas P. Moeck
Keyword(s):  
Experimental Data ◽  
Numerical Analysis ◽  
Network Model ◽  
Rotational Symmetry ◽  
Stability Criteria ◽  
Describing Function ◽  
Modal Interactions ◽  
Dynamical Features ◽  
Theoretical And Numerical Analysis ◽  
Flame Describing Function

In this theoretical and numerical analysis, a low-order network model is used to investigate a thermoacoustic system with discrete rotational symmetry. Its geometry resembles that of the MICCA combustor (Laboratoire EM2C, CentraleSupelec); the flame describing function (FDF) employed in the analysis is that of a single-burner configuration and is taken from experimental data reported in the literature. We show how most of the dynamical features observed in the MICCA experiment, including the so-called slanted mode, can be predicted within this framework, when the interaction between a longitudinal and an azimuthal thermoacoustic mode is considered. We show how these solutions relate to the symmetries contained in the equations that model the system. We also discuss how considering situations in which two modes are linearly unstable compromises the applicability of stability criteria available in the literature.

Describing Function Analysis of Limit Cycles in a Multiple Flame Combustor

2010 ◽  
Author(s):  
Fre´de´ric Boudy ◽  
Daniel Durox ◽  
Thierry Schuller ◽  
Grunde Jomaas ◽  
Se´bastien Candel
Keyword(s):  
Transfer Function ◽  
Limit Cycle ◽  
Limit Cycles ◽  
Function Analysis ◽  
Combustion Instabilities ◽  
Describing Function ◽  
Variable Size ◽  
Theoretical Predictions ◽  
Flame Describing Function ◽  
Oscillation Frequencies

A recently developed nonlinear Flame Describing Function (FDF) is used to analyze combustion instabilities in a system where the feeding manifold has a variable size and where the flame is confined by quartz tubes of variable length. Self-sustained combustion oscillations are observed when the geometry is changed. Regimes of oscillation are characterized at the limit cycle and also during the onset of oscillations. Theoretical predictions of the oscillation frequencies and levels are obtained using the FDF. This generalizes the concept of flame transfer function by including a dependence on the frequency and on the level of oscillation. Predictions are compared with experimental results for two different lengths of the confinement tube. These results are in turn used to predict most of the experimentally observed phenomena and in particular the correct oscillation levels and frequencies at limit cycles.

A Weakly Nonlinear Approach Based on a Distributed Flame Describing Function to Study the Combustion Dynamics of a Full-Scale Lean-Premixed Swirled Burner

2017 ◽  
Vol 139 (9) ◽  
Author(s):  
Davide Laera ◽  
Sergio M. Camporeale
Keyword(s):  
Heat Release ◽  
Limit Cycle ◽  
Heat Release Rate ◽  
Release Rate ◽  
Gas Turbines ◽  
Full Scale ◽  
Describing Function ◽  
Weakly Nonlinear ◽  
Lean Premixed ◽  
Flame Describing Function

Modern combustion chambers of gas turbines for power generation and aero-engines suffer of thermo-acoustic combustion instabilities generated by the coupling of heat release rate fluctuations with pressure oscillations. The present article reports a numerical analysis of limit cycles arising in a longitudinal combustor. This corresponds to experiments carried out on the longitudinal rig for instability analysis (LRIA) test facility equipped with a full-scale lean-premixed burner. Heat release rate fluctuations are modeled considering a distributed flame describing function (DFDF), since the flame under analysis is not compact with respect to the wavelengths of the unstable modes recorded experimentally. For each point of the flame, a saturation model is assumed for the gain and the phase of the DFDF with increasing amplitude of velocity fluctuations. A weakly nonlinear stability analysis is performed by combining the DFDF with a Helmholtz solver to determine the limit cycle condition. The numerical approach is used to study two configurations of the rig characterized by different lengths of the combustion chamber. In each configuration, a good match has been found between numerical predictions and experiments in terms of frequency and wave shape of the unstable mode. Time-resolved pressure fluctuations in the system plenum and chamber are reconstructed and compared with measurements. A suitable estimate of the limit cycle oscillation is found.

Nonlinear Flame Describing Function Analysis of Galloping Limit Cycles Featuring Chaotic States in Premixed Combustors

2012 ◽  
Author(s):  
Frédéric Boudy ◽  
Daniel Durox ◽  
Thierry Schuller ◽  
Sébastien Candel
Keyword(s):  
Limit Cycle ◽  
Limit Cycles ◽  
Function Analysis ◽  
Perforated Plate ◽  
Operating Conditions ◽  
Nonlinear Prediction ◽  
Constant Amplitude ◽  
Describing Function ◽  
Flame Describing Function ◽  
Velocity Pressure

Nonlinear prediction of combustion instabilities in premixed systems is undertaken on a generic configuration featuring an adjustable feeding manifold length, a multipoint injector composed of a perforated plate and a flame confinement tube. By changing the feeding manifold or flame tube lengths, the system exhibits different types of combustion regimes for the same flow operating conditions. Velocity, pressure and heat release rate measurements are used to examine oscillations during unstable operation. For many operating conditions, a limit cycle is reached at an essentially fixed oscillation frequency and quasi-constant amplitude. In another set of cases, the system features other types of oscillations characterized by multiple frequencies, amplitude modulation and irregular bursts which can be designated by “galloping” limit cycles or GLC. These situations are explored in this article. Imaging during GLCs indicates that the flame is globally oscillating but that the cycle is irregular. Prediction of these special oscillation states is tackled within the Flame Describing Function (FDF) framework. It is shown that it is possible to predict with a reasonable degree of agreement the ranges where a quasi-constant amplitude limit cycle will be established and ranges where the oscillation will be less regular and take the form of a galloping limit cycle. It is found that the FDF analysis also provides indications on the bounding levels of the oscillation envelope in the latter case.

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