Tuning of the Acoustic Boundary Conditions of Combustion Test Rigs With Active Control: Extension to Actuators With Nonlinear Response

2010 ◽  
Vol 132 (9) ◽  
Author(s):  
Mirko R. Bothien ◽  
Christian Oliver Paschereit
Keyword(s):  
Boundary Conditions ◽  
Active Control ◽  
Nonlinear Response ◽  
Combustion Process ◽  
Full Scale ◽  
Operating Conditions ◽  
Test Rig ◽  
Acoustic Boundary Conditions ◽  
Control Scheme ◽  
Resonance Frequencies

In the design process, new burners are generally tested in combustion test rigs. With these experiments, as well as with computational fluid dynamics, finite element calculations, and low-order network models, the burner’s performance in the full-scale engine is sought to be predicted. Especially, information about the thermoacoustic behavior and the emissions is very important. As the thermoacoustics strongly depend on the acoustic boundary conditions of the system, it is obvious that test rig conditions should match or be close to those of the full-scale engine. This is, however, generally not the case. Hence, if the combustion process in the test rig is stable at certain operating conditions, it may show unfavorable dynamics at the same conditions in the engine. In previous works, the authors introduced an active control scheme, which is able to mimic almost arbitrary acoustic boundary conditions. Thus, the test rig properties can be tuned to correspond to those of the full-scale engine. The acoustic boundary conditions were manipulated using woofers. In the present study, an actuator with higher control authority is investigated, which could be used to apply the control scheme in industrial test rigs. The actuator modulates an air mass flow to generate an acoustic excitation. However, in contrast to the woofers, it exhibits a strong nonlinear response regarding amplitude and frequency. Thus, the control scheme is further developed to account for these nonlinear transfer characteristics. This modified control scheme is then applied to change the acoustic boundary conditions of an atmospheric swirl-stabilized combustion test rig. Excellent results were obtained in terms of changing the reflection coefficient to different levels. By manipulating its phase, different resonance frequencies could be imposed without any hardware changes. The nonlinear control approach is not restricted to the actuator used in this study and might therefore be of use for other actuators as well.

Active Control of the Acoustic Boundary Conditions of Combustion Test Rigs: Extension to Actuators With Non-Linear Response

2009 ◽  
Author(s):  
Mirko R. Bothien ◽  
Christian Oliver Paschereit
Keyword(s):  
Boundary Conditions ◽  
Active Control ◽  
Linear Response ◽  
Full Scale ◽  
Operating Conditions ◽  
Test Rig ◽  
Acoustic Boundary Conditions ◽  
Control Scheme ◽  
Resonance Frequencies ◽  
Non Linear

In the design process, new burners are generally tested in combustion test rigs. With these experiments, as well as with CFD, finite element calculations, and low-order network models, the burner’s performance in the full-scale engine is sought to be predicted. Especially, information about the thermoacoustic behaviour and the emissions is very important. As the thermoacoustics strongly depend on the acoustic boundary conditions of the system, it is obvious that test rig conditions should match or be close to those of the full-scale engine. This is, however, generally not the case. Hence, if the combustion process in the test rig is stable at certain operating conditions, it may show unfavourable dynamics at the same conditions in the engine. In previous works, the authors introduced an active control scheme which is able to mimic almost arbitrary acoustic boundary conditions. Thus, the test rig properties can be tuned to correspond to those of the full-scale engine. The acoustic boundary conditions were manipulated using woofers. In the present study, an actuator with higher control authority is investigated, which could be used to apply the control scheme in industrial test rigs. The actuator modulates an air mass flow to generate an acoustic excitation. However, in contrast to the woofers, it exhibits a strong non-linear response regarding amplitude and frequency. Thus, the control scheme is further developed to account for these non-linear transfer characteristics. This modified control scheme is then applied to change the acoustic boundary conditions of an atmospheric swirl-stabilized combustion test rig. Excellent results were obtained in terms of changing the reflection coefficient to different levels. By manipulating its phase, different resonance frequencies could be imposed without any hardware changes. The non-linear control approach is not restricted to the actuator used in this study and might therefore be of use for other actuators as well.

Assessment of Different Actuator Concepts for Acoustic Boundary Control of a Premixed Combustor

2008 ◽  
Vol 131 (2) ◽  
Author(s):  
Mirko R. Bothien ◽  
Jonas P. Moeck ◽  
Christian Oliver Paschereit
Keyword(s):  
Boundary Conditions ◽  
Combustion Process ◽  
Industrial Applications ◽  
Full Scale ◽  
Operating Conditions ◽  
Test Rig ◽  
Acoustic Boundary Conditions ◽  
Control Scheme ◽  
Finite Element Calculations ◽  
Control Authority

In the design process, new burners are generally tested in combustion test rigs. With these experiments, computational fluid dynamics, and finite element calculations, the burners’ performance in the full-scale engine is sought to be predicted. Especially, information about the thermoacoustic behavior and the emissions is very important. As the thermoacoustics strongly depend on the acoustic boundary conditions of the system, it is obvious that test rig conditions should match or be close to those of the full-scale engine. This is, however, generally not the case. Hence, if the combustion process in the test rig is stable at certain operating conditions, it may show unfavorable dynamics at the same conditions in the engine. In previous works, the authors introduced an active control scheme, which is able to mimic almost arbitrary acoustic boundary conditions. Thus, the test rig properties can be tuned to correspond to those of the full-scale engine. The acoustic boundary conditions were manipulated using woofers. In the present study, proportional valves are investigated regarding their capabilities of being used in the control scheme. It is found that the test rig impedance can be tuned equally well. In contrast to the woofers, however, the valves could be used in industrial applications, as they are more robust and exhibit more control authority. Additionally, the control scheme is further developed and used to tune the test rig at discrete frequencies. This exhibits certain advantages compared with the case of control over a broad frequency band.

Assessment of Different Actuator Concepts for Acoustic Boundary Control of a Premixed Combustor

2008 ◽  
Author(s):  
Mirko R. Bothien ◽  
Jonas P. Moeck ◽  
Christian Oliver Paschereit
Keyword(s):  
Boundary Conditions ◽  
Combustion Process ◽  
Industrial Applications ◽  
Full Scale ◽  
Operating Conditions ◽  
Test Rig ◽  
Acoustic Boundary Conditions ◽  
Control Scheme ◽  
Finite Element Calculations ◽  
Control Authority

In the design process, new burners are generally tested in combustion test rigs. With these experiments, computational fluid dynamics, and finite element calculations, the burners’ performance in the full-scale engine is sought to be predicted. Especially, information about the thermoacoustic behavior and the emissions is very important. As the thermoacoustics strongly depend on the acoustic boundary conditions of the system, it is obvious that test rig conditions should match or be close to those of the full-scale engine. This is, however, generally not the case. Hence, if the combustion process in the test rig is stable at certain operating conditions, it may show unfavorable dynamics at the same conditions in the engine. In a previous paper (GT2007-27796), the authors introduced an active control scheme which is able to mimic almost arbitrary acoustic boundary conditions. Thus, the test rig properties can be tuned to correspond to those of the full-scale engine. The acoustic boundary conditions were manipulated using woofers. In the present study, proportional valves are investigated regarding their capabilities of being used in the control scheme. It is found that the test rig impedance can be tuned equally well. In contrast to the woofers, however, the valves could be used in industrial applications, as they are more robust and exhibit more control authority. Additionally, the control scheme is further developed and used to tune the test rig at discrete frequencies. This exhibits certain advantages compared to the case of control over a broad frequency band.

Impedance Tuning of a Premixed Combustor Using Active Control

2007 ◽  
Author(s):  
Mirko R. Bothien ◽  
Jonas P. Moeck ◽  
Christian Oliver Paschereit
Keyword(s):  
Boundary Conditions ◽  
Combustion Chamber ◽  
Active Control ◽  
Combustion Process ◽  
Reacting Flow ◽  
Acoustic Behavior ◽  
Acoustic Boundary Conditions ◽  
Early Design ◽  
Resonance Frequencies ◽  
Arbitrary Frequency

In early design phases new burner concepts are mostly tested in single or multi burner test rigs. These test rigs generally exhibit a different acoustic behavior than the full scale engine. The acoustic behavior, however, is crucial to predict whether thermoacoustic instabilities are likely to occur. Tuning the test rig’s acoustic boundary conditions to that of the engine could overcome this issue. Through this, an effective assessment of new burners is possible even in early design phases. In this work a method is proposed, which uses an active control scheme to manipulate the acoustic boundary conditions. It is applied to an atmospheric combustor test rig with a swirl-stabilized burner. In a first step it is shown that the acoustic boundary conditions can be controlled in the cold flow case. Almost arbitrary frequency dependent impedances can be prescribed ranging from fully reflecting (both pressure and velocity node) to anechoic. In particular, an additional virtual length can be added to the combustor outlet by manipulation of the reflection coefficient’s phase. This introduces resonance frequencies different from those of the uncontrolled case. In a second step the impedance tuning concept is applied to the reacting flow. It is demonstrated that the concept is feasible despite the harsh environmental conditions in a combustion chamber. The effect of different levels of reflection at the combustion chamber outlet on the combustion process is investigated. In addition to that, a study of the influence of the simulated combustor length on the system’s resonance frequencies is conducted.

Modelling of Thermoacoustic Combustion Instabilities Phenomena: Application to an Experimental Rig for Testing Full Scale Burners

2014 ◽  
Author(s):  
Davide Laera ◽  
Giovanni Campa ◽  
Sergio M. Camporeale ◽  
Edoardo Bertolotto ◽  
Sergio Rizzo ◽  
...  
Keyword(s):  
Acoustic Analysis ◽  
Fem Analysis ◽  
Full Scale ◽  
Operating Conditions ◽  
System Modelling ◽  
Combustion Instabilities ◽  
Test Rig ◽  
Pressure Oscillations ◽  
Secondary Air ◽  
Actual Geometry

This paper concerns the acoustic analysis of self–sustained thermoacoustic pressure oscillations that occur in a test rig equipped with full scale lean premixed burner. The experimental work is conducted by Ansaldo Energia and CCA (Centro Combustione Ambiente) at the Ansaldo Caldaie facility in Gioia del Colle (Italy), in cooperation with Politecnico di Bari. The test rig is characterized by a longitudinal development with two acoustic volumes, plenum and combustion chamber, coupled by the burner. The length of both chambers can be varied with continuity in order to obtain instability at different frequencies. A previously developed three dimensional finite element code has been applied to carry out the linear stability analysis of the system, modelling the thermoacoustic combustion instabilities through the Helmholtz equation under the hypothesis of low Mach approximation. The heat release fluctuations are modelled according to the κ-τ approach. The burner, characterized by two conduits for primary and secondary air, is simulated by means of both a FEM analysis and a Burner Transfer Matrix (BTM) method in order to examine the influence of details of its actual geometry. Different operating conditions, in which self–sustained pressure oscillations have been observed, are examined. Frequencies and growth rates of unstable modes are identified, with good agreement with experimental data in terms of frequencies and acoustics pressure wave profiles.

Demonstration of Active Control of Combustion Instabilities on a Full-Scale Gas Turbine Combustor

2001 ◽  
Author(s):  
C. E. Johnson ◽  
Y. Neumeier ◽  
M. Neumaier ◽  
B. T. Zinn ◽  
D. D. Darling ◽  
...  
Keyword(s):  
Gas Turbine ◽  
Active Control ◽  
Fast Response ◽  
Dominant Mode ◽  
Broadband Noise ◽  
Full Scale ◽  
Operating Conditions ◽  
Combustion Instabilities ◽  
Gas Turbine Combustor ◽  
Airflow Distribution

This paper presents the results of an investigation of active control of combustion instabilities in a natural gas, high-pressure, full-scale gas turbine combustor that was retrofitted with an Active Control System (ACS). The combustor test rig simulates the geometry, inlet airflow distribution, and pressurization of a can-type combustor that exhibits dynamic flame instabilities at some off-design operating conditions. Two essential features of the investigated ACS are 1) a real-time mode observer that identified the frequencies, amplitudes and phases of the dominant modes in the pressure signal and 2) a fast response servo valve that can modulate a large portion of the gaseous fuel. Two active control configurations were studied. In the first configuration, the actuator was mounted on one of two premixed fuel stages, and in the second configuration it was mounted on the inlet to the stabilizing diffusion stage. In both configurations, the ACS damped combustion instabilities, attenuating the dominant mode by up to 15dB and reducing the overall broadband noise by 30-40%. NOx emissions were also reduced by approximately 10% when control was applied. Finally, this study demonstrated the importance of having a fast multiple-mode observer when dealing with complex combustion processes with inherently large time delays.

Wave Rotor Combustor Test Rig Preliminary Design

2004 ◽  
Author(s):  
Berrak Alparslan ◽  
M. Razi Nalim ◽  
Philip H. Snyder
Keyword(s):  
Computational Models ◽  
Combustion Process ◽  
Constant Volume ◽  
Operating Conditions ◽  
Experimental Program ◽  
Preliminary Design ◽  
Wave Rotor ◽  
Test Rig ◽  
Operating Cycle ◽  
And Performance

Pressure gain combustion in a wave rotor approaching the thermodynamic ideal of constant volume combustion has been proposed to significantly enhance the performance of gas turbine engines. A computational and experimental program is currently being conducted to investigate the combustion process and performance of a wave rotor with detonative and near-detonative internal combustion. An innovative and flexible preliminary design of the test rig is presented to demonstrate the operation and performance of the system. A preliminary design method based on a sequence of computational models is used to design wave processes for testing in the rig and to define rig geometry and operating conditions. The operating cycle allows for propagation of the combustion front from the exit end of the combustion channel to the inlet end. This is similar to and motivated by the Constant Volume Combustor (CVC) concept that seeks to produce a relatively uniform set of outflow conditions in both spatial and time coordinates.

Forced Response of Mistuned Bladed Discs in Gas Flow: A Comparative Study of Predictions and Full-Scale Experimental Results

2009 ◽  
Author(s):  
Evgeny Petrov ◽  
Luca Di Mare ◽  
Holger Hennings ◽  
Robert Elliott
Keyword(s):  
Data Exchange ◽  
Gas Flow ◽  
Numerical Study ◽  
Forced Response ◽  
Full Scale ◽  
Response Analysis ◽  
Test Rig ◽  
Good Correspondence ◽  
Resonance Frequencies ◽  
Underplatform Damper

An integrated experimental-numerical study of forced response for a mistuned bladed disc has been performed. A full chain for the predictive forced response analysis has been developed including data exchange between the CFD code and a code for the prediction of the nonlinear forced response for a bladed disc. The experimental measurements are performed at a full-scale single stage test rig with excitation by aerodynamic forces from gas flow. Numerical modelling approaches and the test rig setup are discussed. Comparison of experimentally measured and predicted values of blade resonance frequencies and response levels for a mistuned bladed disc without dampers is performed. A good correspondence between frequencies at which individual blades have maximum response levels is achieved. The effects of structural damping and underplatform damper parameters on amplitudes and resonance frequencies of the bladed disc are explored. It is shown that the underplatform damper significantly reduces scatters in values of the individual blade frequencies and maximum forced response levels.

Forced Response of Mistuned Bladed Disks in Gas Flow: A Comparative Study of Predictions and Full-Scale Experimental Results

2010 ◽  
Vol 132 (5) ◽  
Author(s):  
Evgeny Petrov ◽  
Luca Di Mare ◽  
Holger Hennings ◽  
Robert Elliott
Keyword(s):  
Data Exchange ◽  
Gas Flow ◽  
Numerical Study ◽  
Forced Response ◽  
Full Scale ◽  
Response Analysis ◽  
Test Rig ◽  
Bladed Disk ◽  
Resonance Frequencies ◽  
Underplatform Damper

An integrated experimental-numerical study of forced response for a mistuned bladed disk has been performed. A full chain for the predictive forced response analysis has been developed including data exchange between the computational fluid dynamics code and a code for the prediction of the nonlinear forced response for a bladed disk. The experimental measurements are performed at a full-scale single stage test rig with excitation by aerodynamic forces from gas flow. The numerical modeling approaches and the test rig setup are discussed. Comparison of experimentally measured and predicted values of blade resonance frequencies and response levels for a mistuned bladed disk without dampers is performed. A good correspondence between frequencies at which individual blades have maximum response levels is achieved. The effects of structural damping and underplatform damper parameters on amplitudes and resonance frequencies of the bladed disk are explored. It is shown that the underplatform damper significantly reduces scatters in values of the individual blade frequencies and maximum forced response levels.

Thermoacoustic Analysis of Gas Turbine Combustion Systems Using Unsteady CFD

2005 ◽  
Author(s):  
Bruno Schuermans ◽  
Holger Luebcke ◽  
Denis Bajusz ◽  
Peter Flohr
Keyword(s):  
Transfer Function ◽  
Boundary Conditions ◽  
Gas Turbine ◽  
Network Model ◽  
Full Scale ◽  
Test Facility ◽  
Combustion System ◽  
Acoustic Boundary Conditions ◽  
Gas Turbine Combustion ◽  
Gas Turbine Burner

Unsteady Computational Fluid Dynamics (CFD) has been used to predict thermoacoustic interaction processes in an industrial gas turbine burner. Because detailed unsteady simulation of an entire gas turbine combustion system is forbiddingly expensive, two different approaches have been applied to overcome this problem. In the first approach, time-domain acoustic boundary conditions are applied to the computational domain of the CFD. The idea is to model in CFD only that part of the problem that cannot be represented by low order (acoustic) models. The advantage is not only that the method is much faster; it also allows changes in acoustic boundary conditions without a need to make a new mesh for the problem. This method introduced here is novel and can be used to apply any (causal) acoustic impedance matrix to a CFD computation. The desired impedance can either be obtained analytically, from an acoustic network model or from an acoustic finite element code. The method has been tested on various test cases and proved to be accurate and robust. First, a simple duct with non reactive flow has been simulated. A non refelecting boundary condition for plane waves has been applied. In a further step the methodology was implemented on a gas turbine burner with combustion. The measured acoustic boundary conditions of a single burner test facility have been applied. The predicted pressure spectra are in reasonable agreement with measured pulsation spectra of a full-scale gas turbine burner in an atmospheric combustion test facility. In the second approach a system identification technique is used in a post-processing step of the CFD results. In this way the transfer function relating the acoustic quantities on both sides of the flame is obtained. This transfer function can then be applied to an acoustic network model of the system. The advantage of this method is that once the transfer matrix of the combustion zone is obtained, the influence of combustion system geometry can be investigated in the low order model, which is very fast. This method has been compared with measured transfer matrices of a full-scale swirl stabilized gas turbine burner and proved to be in good agreement.

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