Nonlinear Flame Transfer Function Characteristics in a Swirl-Stabilized Combustor

2006 ◽  
Vol 129 (4) ◽  
pp. 954-961 ◽  
Author(s):  
Benjamin D. Bellows ◽  
Mohan K. Bobba ◽  
Jerry M. Seitzman ◽  
Tim Lieuwen
Keyword(s):  
Nonlinear Response ◽  
Amplitude Dependence ◽  
Acoustic Excitation ◽  
Acoustic Oscillations ◽  
Flame Dynamics ◽  
Large Velocity ◽  
Planar Laser ◽  
Flame Response ◽  
Test Points ◽  
Unsteady Flame

An understanding of the amplitude dependence of the flame response to acoustic excitation is required in order to predict and/or correlate combustion instability amplitudes. This paper describes an experimental investigation of the nonlinear response of a lean, premixed flame to imposed acoustic oscillations. Detailed measurements of the amplitude dependence of the flame response were obtained at approximately 100 test points, corresponding to different flow rates and forcing frequencies. It is observed that the nonlinear flame response can exhibit a variety of behaviors, both in the shape of the response curve and the forcing amplitude at which nonlinearity is first observed. The phase between the flow oscillation and heat release is also seen to have substantial amplitude dependence. The nonlinear flame dynamics appear to be governed by different mechanisms in different frequency and flowrate regimes. These mechanisms were investigated using phase-locked, two- dimensional OH Planar laser-induced fluorescence imaging. From these images, two mechanisms, vortex rollup and unsteady flame liftoff, are identified as important in the saturation of the flame’s response to large velocity oscillations. Both mechanisms appear to reduce the flame’s area and thus its response at these high levels of driving.

Nonlinear Flame Transfer Function Characteristics in a Swirl-Stabilized Combustor

2006 ◽  
Author(s):  
Benjamin D. Bellows ◽  
Mohan K. Bobba ◽  
Jerry M. Seitzman ◽  
Tim Lieuwen
Keyword(s):  
Nonlinear Response ◽  
Amplitude Dependence ◽  
Acoustic Excitation ◽  
Acoustic Oscillations ◽  
Flow Oscillation ◽  
Flame Dynamics ◽  
Large Velocity ◽  
Flame Response ◽  
Test Points ◽  
Unsteady Flame

An understanding of the amplitude dependence of the flame response to acoustic excitation is required in order to predict and/or correlate combustion instability amplitudes. This paper describes an experimental investigation of the nonlinear response of a lean, premixed flame to imposed acoustic oscillations. Detailed measurements of the amplitude dependence of the flame response were obtained at approximately 100 test points, corresponding to different flow rates and forcing frequencies. It is observed that the nonlinear flame response can exhibit a variety of behaviors, both in the shape of the response curve and the forcing amplitude at which nonlinearity is first observed. The phase between the flow oscillation and heat release is also seen to have substantial amplitude dependence. The nonlinear flame dynamics appear to be governed by different mechanisms in different frequency and flowrate regimes. These mechanisms were investigated using phase-locked, two-dimensional OH PLIF imaging. From these images, two mechanisms, vortex rollup and unsteady flame liftoff, are identified as important in the saturation of the flame’s response to large velocity oscillations. Both mechanisms appear to reduce the flame’s area and thus its response at these high levels of driving.

Nonlinear Heat-Release/Acoustic Interactions in a Gas Turbine Combustor

2004 ◽  
Author(s):  
Ben Bellows ◽  
Tim Lieuwen
Keyword(s):  
Transfer Function ◽  
Heat Release ◽  
Gas Turbines ◽  
Laminar Flame ◽  
Turbulent Flame ◽  
Amplitude Dependence ◽  
Acoustic Oscillations ◽  
Bunsen Flame ◽  
Flame Response ◽  
Acoustic Transfer Function

This paper describes an experimental investigation of the response of the flame in a lean, premixed combustor to imposed acoustic oscillations. The ultimate objective of this work is to develop capabilities for predicting the amplitude of combustion instabilities in gas turbines. Simultaneous measurements of CH* and OH* chemiluminescence, pressure, and velocity were obtained over a range of forcing amplitudes and frequencies. These data show that nonlinearity in the heat release/acoustic transfer function is manifested in two ways. First, the flame chemiluminescence response to imposed oscillations saturates at pressure and velocity amplitudes on the order of p’/po ∼0.02 and u’/uo∼0.3. In addition, the phase between the CH* or OH* oscillations and acoustic oscillations exhibits some amplitude dependence, even at disturbance amplitudes where the amplitude transfer function is linear. We also find that the response of this swirling, highly turbulent flame exhibits similarities to those of simple, laminar flame configurations. First, the “linear”, low amplitude flame response is similar to the laminar, V-flame measurements and predictions of Schuller et al. [1]. Also, at large disturbance amplitudes, the subharmonic characteristics of the oscillations exhibit analogous characteristics to those observed by Bourehla & Baillot [2] in a conical Bunsen flame, and Searby & Rochwerger [3] in a flat flame.

scholarly journals Flame response to high-frequency oscillations in a cryogenic oxygen/hydrogen rocket combustor

2019 ◽  
Author(s):  
N. Fdida ◽  
J. Hardi ◽  
H. Kawashima ◽  
B. Knapp ◽  
M. Oschwald ◽  
...  
Keyword(s):  
High Frequency ◽  
Acoustic Resonance ◽  
High Amplitude ◽  
Operating Conditions ◽  
Test Facility ◽  
Response Analysis ◽  
Rocket Engines ◽  
Acoustic Oscillations ◽  
Spatially Resolved ◽  
Flame Response

Experiments presented in this paper were conducted with the BKH rocket combustor at the European Research and Technology Test Facility P8, located at DLR Lampoldshausen. This combustor is dedicated to study the effects of high magnitude instabilities on oxygen/hydrogen flames, created by forcing high-frequency (HF) acoustic resonance of the combustion chamber. This work addresses the need for highly temporally and spatially resolved visualization data, in operating conditions representative of real rocket engines, to better understand the flame response to high amplitude acoustic oscillations. By combining ONERA and DLR materials and techniques, the optical setup of this experiment has been improved to enhance the existing database with more highly resolved OH* imaging to allow detailed response analysis of the flame. OH* imaging is complemented with simultaneous visible imaging and compared to each other here for their ability to capture flame dynamics.

Flow Response of an Industrial Gas Turbine Combustor To Acoustic Forcing Extracted From Unforced Data

2021 ◽  
Author(s):  
Jan Paul Beuth ◽  
Jakob G. R. von Saldern ◽  
Thomas Ludwig Kaiser ◽  
Thoralf G. Reichel ◽  
Christian Oliver Paschereit ◽  
...  
Keyword(s):  
Gas Turbine ◽  
Operating Conditions ◽  
Flow Dynamics ◽  
Low Rank ◽  
Frequency Range ◽  
Flow Response ◽  
Flow Fluctuations ◽  
Flame Dynamics ◽  
Flame Response ◽  
Acoustic Forcing

Abstract Gas turbine combustors are commonly operated with lean premix flames, allowing for high efficiencies and low emissions. These operating conditions are susceptible to thermoacoustic pulsations, originating from acoustic-flame coupling. To reveal this coupling, experiments or simulations of acoustically forced combustion systems are necessary, which are very challenging for real-scale applications. In this work we investigate the possibility to determine the flame response to acoustic forcing from snapshots of the unforced flow. This approach is based on three central hypothesis: first, the flame response is driven by flow fluctuations, second, these flow fluctuations are dominated by coherent structures driven by hydrodynamic instabilities, and third, these instabilities are driven by stochastic forcing of the background turbulence. As a consequence the dynamics in the natural flow should be low-rank and very similar to those of the acoustically forced system. In this work, the methodology is applied to experimental data of an industry-scale swirl combustor. A resolvent analysis is conducted based on the linearized Navier-Stokes equations to assure analytically the low-rank behavior of the flow dynamics. Then, these dynamics are extracted from flow snapshots using spectral proper orthogonal decomposition (SPOD). The extended SPOD is applied to determine the heat release rate fluctuations that are correlated with the flow dynamics. The low-rank flow and flame dynamics determined from the analytic and data-driven approach are then compared to the flow response determined from a classic phase average of the acoustically forced flow, which allow the research hypothesis to be evaluated. It is concluded that for the present combustor, the flow and flame dynamics are low-rank for a wider frequency range and the response to harmonic forcing can be determined quite accurately from unforced snapshots. The methodology further allows to isolate the frequency range where the flame response is predominantly driven by hydrodynamic instabilites.

Laminar Microjet Diffusion Flame Response to Transverse Acoustic Excitation

2020 ◽  
Vol 192 (7) ◽  
pp. 1292-1319 ◽  
Author(s):  
Hyung Sub Sim ◽  
Andres Vargas ◽  
Dongchan Daniel Ahn ◽  
Ann R. Karagozian
Keyword(s):  
Diffusion Flame ◽  
Acoustic Excitation ◽  
Transverse Acoustic ◽  
Flame Response

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

2013 ◽  
Author(s):  
Stefanie Bade ◽  
Michael Wagner ◽  
Christoph Hirsch ◽  
Thomas Sattelmayer ◽  
Bruno Schuermans
Keyword(s):  
Optimization Procedure ◽  
Parametric Models ◽  
Design Parameters ◽  
Model Parameters ◽  
Geometrical Parameters ◽  
Flame Dynamics ◽  
Stability Model ◽  
Flame Response ◽  
Burner Design ◽  
Acoustic Stability

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 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 a significant variability of dynamical flame response in dependence of two geometrical parameters. In this paper the experimentally determined complex burner acoustics and complex flame responses are described in terms of physics based parametric models with excellent agreement between experimental and model data. It is shown that these model parameters correlate uniquely with the variation of the burner geometrical parameters, allowing to interpolate the model with respect to the geometrical parameters. The interpolation is validated with experimental data.

Binder/Filler Interaction and the Nonlinear Behavior of Highly-Filled Elastomers

1990 ◽  
Vol 63 (4) ◽  
pp. 488-502 ◽  
Author(s):  
R. G. Stacer ◽  
C. Hübner ◽  
D. M. Husband
Keyword(s):  
Surface Area ◽  
Strain Amplitude ◽  
Nonlinear Response ◽  
Volume Fraction ◽  
Viscoelastic Behavior ◽  
Interaction Model ◽  
Nonlinear Behavior ◽  
Small Deformation ◽  
Amplitude Dependence ◽  
Filled Rubbers

Abstract 1. The small-deformation-viscoelastic response of elastomers containing nonreinforcing filler has been investigated. Nonlinear viscoelastic behavior was observed as a pronounced strain-amplitude dependence. The degree of this dependence was quantified using a power-law representation as a single nonlinear parameter, m. 2. The magnitude of m was a function of formulation variables. It was found that m increased with the volume fraction and particle size of filler material, as well as the volume fraction of plasticizer. Reduced values of m were observed in the presence of bonding agent and with greater degrees of apparent crosslinking. The latter was controlled in this study through imbalanced urethane cures. 3. Nonlinear behavior of elastomers containing nonreinforcing filler has been compared and contrasted with the data base for carbon-black-reinforced elastomers. The major difference is in the effect of the surface area of filler particles. Nonlinear response in black-filled rubbers increases with surface area, while the opposite is reported in this study. Additionally, the relationship between viscoelastic dissipation and the magnitude of nonlinear response, well established for black-filled rubbers, was not observed. These results indicate that the response of elastomers containing nonreinforcing filler, although nearly identical in appearance to that seen with reinforcing filler, is not driven by the same mechanism. 4. A binder/filler interaction model is proposed for materials containing nonreinforcing filler. This model is based on the ideal adhesive strength of the binder/filler interface. In this model, greater attraction between polymer and particle surfaces reduces molecular slippage during deformation, leading to a decreased dependence of the modulus on strain amplitude, or decreased nonlinearity. It is shown that the model provides reasonable predictions for the observed phenomena.

Nonlinear response of buoyant diffusion flame under acoustic excitation

Fuel ◽  
2013 ◽  
Vol 103 ◽  
pp. 364-372 ◽  
Author(s):  
Qian Wang ◽  
Hua Wei Huang ◽  
Hao Jie Tang ◽  
Min Zhu ◽  
Yang Zhang
Keyword(s):  
Diffusion Flame ◽  
Nonlinear Response ◽  
Acoustic Excitation

scholarly journals One-dimensional model describing eigenmode frequency shift during transverse excitation

2019 ◽  
Author(s):  
S. Webster ◽  
J. Hardi ◽  
M. Oschwald
Keyword(s):  
Frequency Shift ◽  
High Amplitude ◽  
Operating Conditions ◽  
Model Parameters ◽  
Amplitude Dependence ◽  
Acoustic Oscillations ◽  
One Dimensional ◽  
Hypothesis Model ◽  
The Time Domain ◽  
Combustion Tests

A shift in transverse eigenmode frequency was observed in an experimental combustion chamber when exposed to large amplitude acoustic oscillations during oxygen–hydrogen combustion tests. A shift in eigenmode frequency under acoustic conditions representative of combustion conditions is of critical importance when tuning acoustic absorbers or investigating injection coupled combustion instabilities. The experimentally observed frequency shift was observed both in the frequency domain and as an asymmetric amplitude response to a linear frequency ramp of an external excitation system in the time domain. The frequency shift was found to be dependent on amplitude and operating condition. A hypothesis is presented for the frequency shift based on change in speed-of-sound distributions due to flame contraction when exposed to high amplitude pressure oscillations. A one-dimensional (1D) model was created to test the hypothesis. Model parameters were based on relationships observed in experimental data. The model was found to accurately recreate the frequency shifting asymmetric response observed in test data as well as its amplitude dependence. Further development is required to investigate the influence of operating conditions and chamber design on the quantitative modeling of the frequency shift.

Sign in / Sign up

Export Citation Format

Share Document