On the Use of Thermoacoustic Analysis for Robust Burner Design

2008 ◽  
Vol 130 (3) ◽  
Author(s):  
Valter Bellucci ◽  
Dariusz Nowak ◽  
Weiqun Geng ◽  
Christian Steinbach
Keyword(s):  
First Generation ◽  
Transfer Functions ◽  
Three Dimensional ◽  
Development Program ◽  
Network Models ◽  
Limiting Factor ◽  
Thermoacoustic Instabilities ◽  
Flame Response ◽  
Burner Design ◽  
Analysis Mode

Advanced thermoacoustic analysis is now routinely used in gas turbine combustor development. A thermoacoustic approach based on a combination of numerical analysis (CFD and three-dimensional acoustics), acoustic network models, and dedicated measurements of acoustic flame response is well accepted across the industry. However, its application to specific combustor upgrade or development programs in “prediction mode” as opposed to “analysis mode” remains a challenge. This is mainly due to the large sensitivity of the complex methodology to key inputs, such as flame transfer functions, that can be only predicted in the burner design phase. This paper discusses an example where we made an effort to apply the thermoacoustic approach in predictive mode. The example refers to the upgrade of a first generation diffusion burner with a partially premix burner to achieve low emissions. Thermoacoustic instabilities were predicted as a limiting factor for combustor operation and thus a design parameter was identified to perform the thermoacoustic combustor tuning at engine level. A particular challenge of this development program was that no test rig was available. Therefore, the new premix burner was directly installed into a field engine where it was successfully tested.

Using Thermoacoustic Analysis for Robust Burner Design

2007 ◽  
Author(s):  
Valter Bellucci ◽  
Dariusz Nowak ◽  
Weiqun Geng ◽  
Christian Steinbach
Keyword(s):  
First Generation ◽  
Transfer Functions ◽  
Three Dimensional ◽  
Development Program ◽  
Network Models ◽  
Limiting Factor ◽  
Thermoacoustic Instabilities ◽  
Flame Response ◽  
Burner Design ◽  
Analysis Mode

Advanced thermoacoustic analysis is now routinely used in gas turbine combustor development. A thermoacoustic approach based on a combination of numerical analysis (CFD and three-dimensional acoustics), acoustic network models and dedicated measurements of acoustic flame response is well accepted across the industry. However, its application to specific combustor upgrade or development programs in “prediction mode” as opposed to “analysis mode” remains a challenge. This is mainly due to the large sensitivity of the complex methodology to key inputs, such as flame transfer functions, that can be only predicted in the burner design phase. This paper discusses an example where we made an effort to apply the thermoacoustic approach in predictive mode. The example refers to the upgrade of a first generation diffusion burner with a partially premix burner to achieve low emissions. Thermoacoustic instabilities were predicted as a limiting factor for combustor operation and thus a design parameter was identified to perform the thermoacoustic combustor tuning at engine level. A particular challenge of this development program was that no test rig was available. Therefore, the new premix burner was directly installed into a field engine where it was successfully tested.

Ranking of Aircraft Fuel-Injectors Regarding Low Frequency Thermoacoustics Based on an Energy Balance Method

2021 ◽  
Author(s):  
André Fischer ◽  
Claus Lahiri
Keyword(s):  
Energy Balance ◽  
Low Frequency ◽  
Network Models ◽  
Operating Conditions ◽  
Balance Method ◽  
Energy Balance Method ◽  
Fuel Injectors ◽  
Thermoacoustic Instabilities ◽  
Aircraft Fuel ◽  
Flame Response

Abstract Many modern low emission combustion systems suffer from thermoacoustic instabilities, which may lead to customer irritation (noise) or engine damages. The prediction of the frequency response of the flame is oftentimes not straightforward, so that it is common practice to measure the flame response in an experiment. The outcome of the measurement is typically a flame transfer-function (FTF), which can be used in low order acoustic network models to represent the flame. This paper applies an alternative criterion to evaluate the potential of the flame to become instable, the flame-amplification factor (FAF). It is based on an energy balance method and can be directly derived from the measured flame-transfer-matrix (FTM). In order to demonstrate this approach two different kerosene-driven aircraft fuel injectors were measured in the Rolls-Royce SCARLET rig in a single-sector RQL-combustor under realistic operating conditions. Here the multi-microphone method has been applied with acoustic forcing from up- and downstream side to determine the FTM. In contrast to the FTF-approach the full FTM data has been post-processed to derive the FAF. The FAF is then successfully used to rank the fuel injectors regarding their low frequency thermo-acoustic behaviour, because it is proportional to amplitudes of self-excited frequencies in FANN-rig (full annular) configuration.

An Experimental Investigation of the Nonlinear Response of an Atmospheric Swirl-Stabilized Premixed Flame

2011 ◽  
Vol 133 (10) ◽  
Author(s):  
Sebastian Schimek ◽  
Jonas P. Moeck ◽  
Christian Oliver Paschereit
Keyword(s):  
Gas Turbines ◽  
Oscillation Amplitude ◽  
Network Models ◽  
Mean Flow ◽  
Test Rig ◽  
Linear Network ◽  
Modeling Tools ◽  
Velocity Fluctuations ◽  
Thermoacoustic Instabilities ◽  
Flame Response

Due to stringent emission restrictions, modern gas turbines mostly rely on lean premixed combustion. Since this combustion mode is susceptible to thermoacoustic instabilities, there is a need for modeling tools with predictive capabilities. Linear network models are able to predict the occurrence of thermoacoustic instabilities but yield no information on the oscillation amplitude. The prediction of the pulsation levels and hence an estimation whether a certain operating condition has to be avoided is only possible if information on the nonlinear flame response is available. Typically, the flame response shows saturation at high forcing amplitudes. A newly constructed atmospheric test rig, specifically designed for the realization of high excitation amplitudes over a broad frequency range, is used to generate extremely high acoustic forcing power with velocity fluctuations of up to 100% of the mean flow. The test rig consists of a generic combustor with a premixed swirl-stabilized natural gas flame, where the upstream part has a variable length to generate adaptive resonances of the acoustic field. The OH∗ chemiluminescence response, with respect to velocity fluctuations at the burner, is measured for various excitation frequencies and amplitudes. From these measurements, an amplitude dependent flame transfer function is obtained. Phase-averaged OH∗ pictures are used to identify changes in the flame shape related to saturation mechanisms. For different frequency regimes, different saturation mechanisms are identified.

An Experimental Investigation of the Nonlinear Response of an Atmospheric Swirl-Stabilized Premixed Flame

2010 ◽  
Author(s):  
Sebastian Schimek ◽  
Jonas P. Moeck ◽  
Christian Oliver Paschereit
Keyword(s):  
Gas Turbines ◽  
Oscillation Amplitude ◽  
Network Models ◽  
Mean Flow ◽  
Test Rig ◽  
Linear Network ◽  
Modeling Tools ◽  
Velocity Fluctuations ◽  
Thermoacoustic Instabilities ◽  
Flame Response

Due to stringent emission restrictions, modern gas turbines mostly rely on lean premixed combustion. Since this combustion mode is susceptible to thermoacoustic instabilities, there is a need for modeling tools with predictive capabilities. Linear network models are able to predict the occurrence of thermoacoustic instabilities but yield no information on the oscillation amplitude. The prediction of the pulsation levels and hence an estimation whether a certain operating condition has to be avoided is only possible if information on the nonlinear flame response is available. Typically, the flame response shows saturation at high forcing amplitudes. A newly constructed atmospheric test rig, specifically designed for the realization of high excitation amplitudes over a broad frequency range, is used to generate extremely high acoustic forcing power with velocity fluctuations of up to 100% of the mean flow. The test rig consists of a generic combustor with a premixed swirl-stabilized natural gas flame, where the upstream part has a variable length to generate adaptive resonances of the acoustic field. The OH* chemiluminescence response, with respect to velocity fluctuations at the burner is measured for various excitation frequencies and amplitudes. From these measurements, an amplitude dependent flame transfer function is obtained. Phase-averaged OH* pictures are used to identify changes in the flame shape related to saturation mechanisms. For different frequency regimes, different saturation mechanisms are identified.

scholarly journals On the 3D → 2D Isomerization of Hexaborane(12)

Chemistry ◽  
2021 ◽  
Vol 3 (1) ◽  
pp. 28-38
Author(s):  
Josep M. Oliva-Enrich ◽  
Ibon Alkorta ◽  
José Elguero ◽  
Maxime Ferrer ◽  
José I. Burgos
Keyword(s):  
Potential Energy ◽  
Potential Energy Surface ◽  
Energy Surface ◽  
Transition States ◽  
Three Dimensional ◽  
Reaction Coordinate ◽  
Intrinsic Reaction Coordinate ◽  
Limiting Factor ◽  
Two Dimensional ◽  
Axis Of Rotation

By following the intrinsic reaction coordinate connecting transition states with energy minima on the potential energy surface, we have determined the reaction steps connecting three-dimensional hexaborane(12) with unknown planar two-dimensional hexaborane(12). In an effort to predict the potential synthesis of finite planar borane molecules, we found that the reaction limiting factor stems from the breaking of the central boron-boron bond perpendicular to the C2 axis of rotation in three-dimensional hexaborane(12).

Acoustic Energy Balance During the Onset, Growth and Saturation of Thermoacoustic Instabilities

2020 ◽  
Author(s):  
R. Gaudron ◽  
D. Yang ◽  
A. S. Morgans
Keyword(s):  
Energy Balance ◽  
Network Models ◽  
Acoustic Energy ◽  
Dimensionless Numbers ◽  
Weakly Nonlinear ◽  
Acoustic Damping ◽  
Thermoacoustic Instabilities ◽  
Wide Range ◽  
Acoustic Absorption Coefficient ◽  
Flame Describing Function

Abstract Thermoacoustic instabilities can occur in a wide range of combustors and are prejudicial since they can lead to increased mechanical fatigue or even catastrophic failure. A well-established formalism to predict the onset, growth and saturation of such instabilities is based on acoustic network models. This approach has been successfully employed to predict the frequency and amplitude of limit cycle oscillations in a variety of combustors. However, it does not provide any physical insight in terms of the acoustic energy balance of the system. On the other hand, Rayleigh’s criterion may be used to quantify the losses, sources and transfers of acoustic energy within and at the boundaries of a combustor. However, this approach is cumbersome for most applications because it requires computing volume and surface integrals and averaging over an oscillation cycle. In this work, a new methodology for studying the acoustic energy balance of a combustor during the onset, growth and saturation of thermoacoustic instabilities is proposed. The two cornerstones of this new framework are the acoustic absorption coefficient Δ and the cycle-to-cycle acoustic energy ratio λ, both of which do not require computing integrals. Used along with a suitable acoustic network model, where the flame frequency response is described using the weakly nonlinear Flame Describing Function (FDF) formalism, these two dimensionless numbers are shown to characterize: 1) the variation of acoustic energy stored within the combustor between two consecutive cycles, 2) the acoustic energy transfers occurring at the combustor’s boundaries and 3) the sources and sinks of acoustic energy located within the combustor. The acoustic energy balance of the well-documented Palies burner is then analyzed during the onset, growth and saturation of thermoacoustic instabilities using this new methodology. It is demonstrated that this new approach allows a deeper understanding of the physical mechanisms at play. For instance, it is possible to determine when the flame acts as an acoustic energy source or sink, where acoustic damping is generated, and if acoustic energy is transmitted through the boundaries of the burner.

Laser Forming for Flexible Fabrication

2000 ◽  
Vol 16 (02) ◽  
pp. 97-109
Author(s):  
Koichi Masubuchi ◽  
Jerry E. Jones
Keyword(s):  
Three Dimensional ◽  
Low Carbon Steel ◽  
High Strength Steels ◽  
Cost Benefit ◽  
Network Models ◽  
High Strength ◽  
Laser Forming ◽  
Low Carbon ◽  
Flat Plates ◽  
Neural Network Models

A 36-month program supported by the Defense Advanced Research Projects Agency (DARPA) was conducted to demonstrate the feasibility to predictably laser form a variety of ferrous and non-ferrous metals of different thickness. Laser forming provides a method of producing complex shapes in sheet, plate, and tubing without the use of tooling, molds, or dies. By heating a localized area with a laser beam, it is possible to create stress states that result in predictable deformation. This research program has developed, refined and demonstrated constitutive and empirical, and neural network models to predict deformation as a function of critical parametric variables and established an understanding of the effect of laser forming on some metallurgical properties of materials. The program was organized into two, time-phased tasks. The first task involved forming flat plates to one-dimensional (I -D) shapes, such as, hinge bends in various materials including low-carbon steel, high-strength steels, nickel-based super alloys, and aluminum alloys. The second task expanded the work conducted in the first task to investigate three-dimensional (3-D) configurations. The models were updated, 3-D specimens fabricated and evaluated, and cost benefit analyses were performed.

Performance Based Evaluation of Bridge Substructure in North Mississippi Using Nonlinear FEM and Field Vibration Measurement

2000 ◽  
Author(s):  
Chris L. Mullen ◽  
Prabin R. Tuladhar
Keyword(s):  
Finite Element ◽  
Transfer Functions ◽  
Response Spectrum ◽  
Three Dimensional ◽  
Vibration Measurement ◽  
Elastic Behavior ◽  
Evaluation Procedure ◽  
Vibration Measurements ◽  
Linear Elastic ◽  
Performance Based Evaluation

Abstract Discussion of a Performance - Based Engineering evaluation procedure for an existing interstate highway bridge in north Mississippi. The bridge is in a highly trafficked location near the Memphis Metropolitan area and is reflective of modern design practices in Mississippi. Results are presented of nonlinear damage response and displacement ductility performance of the reinforced concrete bents and their foundations predicted using static finite element (FE) computations. The model considers the composite action of the concrete and the reinforcing steel materials under axial force, shear, torsion and flexure. The performance-based evaluation includes three-dimensional computational simulations of the nonlinear bridge system, including substructures and superstructure. The response spectrum dynamic analysis method will also be carried out on the linear elastic three-dimensional model to predict the linear elastic behavior. Field vibration measurements, including ambient and hammer-impact, were performed to calibrate the models. The computed transfer functions are currently being evaluated to correlate vibration measurements and the Finite element models.

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