Effects of acoustic liner on thermoacoustic instabilities in a premixed swirl combustor

2021 ◽  
Vol 118 ◽  
pp. 107070
Author(s):  
Liangliang Xu ◽  
Guangyu Zhang ◽  
Guoqing Wang ◽  
Zhenzhen Feng ◽  
Xiaojing Tian ◽  
...  
Keyword(s):  
Swirl Combustor ◽  
Thermoacoustic Instabilities ◽  
Acoustic Liner

Design of Acoustic Liner in Small Gas Turbine Combustor Using One-Dimensional Impedance Models

2018 ◽  
Vol 140 (12) ◽  
Author(s):  
Daesik Kim ◽  
Seungchai Jung ◽  
Heeho Park
Keyword(s):  
Gas Turbine ◽  
Side Wall ◽  
Acoustic Energy ◽  
Gas Turbine Combustor ◽  
Design Guideline ◽  
Acoustic Damping ◽  
Thermoacoustic Instabilities ◽  
Acoustic Dissipation ◽  
Acoustic Liner ◽  
Bias Flow

The side-wall cooling liner in a gas turbine combustor serves main purposes—heat transfer and emission control. Additionally, it functions as a passive damper to attenuate thermoacoustic instabilities. The perforations in the liner mainly convert acoustic energy into kinetic energy through vortex shedding at the orifice rims. In the previous decades, several analytical and semi-empirical models have been proposed to predict the acoustic damping of the perforated liner. In the current study, a few of the models are considered to embody the transfer matrix method (TMM) for analyzing the acoustic dissipation in a concentric tube resonator with a perforated element and validated against experimental data in the literature. All models are shown to quantitatively appropriately predict the acoustic behavior under high bias flow velocity conditions. Then, the models are applied to maximize the damping performance in a realistic gas turbine combustor, which is under development. It is found that the ratio of the bias flow Mach number to the porosity can be used as a design guideline in choosing the optimal combination of the number and diameter of perforations in terms of acoustic damping.

scholarly journals Shape Optimization of Thermoacoustic Systems Using a 2D Adjoint Helmholtz Solver

2020 ◽  
Author(s):  
Stefano Falco ◽  
Matthew Juniper
Keyword(s):  
Shape Optimization ◽  
Longitudinal Mode ◽  
Swirl Combustor ◽  
Rijke Tube ◽  
Thermoacoustic Instabilities ◽  
Iterative Design ◽  
The Mean ◽  
Strong Candidate ◽  
First Time ◽  
Shape Changes

Abstract Thermoacoustic instabilities, which arise due to the interaction between flames and acoustics, are sensitive to small changes to the system parameters. In this paper, we apply adjoint-based shape optimization to a 2D finite element Helmholtz solver to find accurately and inexpensively the shape changes that most stabilise a 2D thermoacoustic system in the linear regime. We examine two cases: a Rijke tube and a turbulent swirl combustor. Both systems exhibit an unstable longitudinal mode and we suppress the instability by slightly modifying the geometry. In the case of the turbulent swirl combustor, the sensitivities are higher in the plenum and in the burner than in the combustion chamber, mainly due to the effect of the mean temperature. In the cooler regions, the local wavelength is shorter, which means that geometry changes of a given distance have more influence than they do where the local wavelength is longer. This is the first time adjoint-based shape optimization is applied to 2D Helmholtz solvers in thermoacoustics, after being previously applied to low-order thermoacoustic networks. But Helmholtz solvers have an intrinsic advantage: they can handle complex geometries. The easy scalability of this method to complex 3D geometries make this tool a strong candidate for the iterative design of thermoacoustically stable combustors.

Shape Optimization of Thermoacoustic Systems Using a 2D Adjoint Helmholtz Solver

2020 ◽  
Author(s):  
Stefano Falco ◽  
Matthew P. Juniper
Keyword(s):  
Shape Optimization ◽  
Longitudinal Mode ◽  
Swirl Combustor ◽  
Rijke Tube ◽  
Thermoacoustic Instabilities ◽  
Iterative Design ◽  
The Mean ◽  
Strong Candidate ◽  
First Time ◽  
Shape Changes

Abstract Thermoacoustic instabilities, which arise due to the interaction between flames and acoustics, are sensitive to small changes to the system parameters. In this paper, we apply adjoint-based shape optimization to a 2D finite element Helmholtz solver to find accurately and inexpensively the shape changes that most stabilise a 2D thermoacoustic system in the linear regime. We examine two cases: a Rijke tube and a turbulent swirl combustor. Both systems exhibit an unstable longitudinal mode and we suppress the instability by slightly modifying the geometry. In the case of the turbulent swirl combustor, the sensitivities are higher in the plenum and in the burner than in the combustion chamber, mainly due to the effect of the mean temperature. In the cooler regions, the local wavelength is shorter, which means that geometry changes of a given distance have more influence than they do where the local wavelength is longer. This is the first time adjoint-based shape optimization is applied to 2D Helmholtz solvers in thermoacoustics, after being previously applied to low-order thermoacoustic networks. But Helmholtz solvers have an intrinsic advantage: they can handle complex geometries. The easy scalability of this method to complex 3D geometries make this tool a strong candidate for the iterative design of thermoacoustically stable combustors.

Suppression of Combustion Instabilities in a Premixed Swirl Combustor With Acoustic Liner

2019 ◽  
Author(s):  
Liangliang Xu ◽  
Guoqing Wang ◽  
Changcai Mo ◽  
Xunchen Liu ◽  
Lei Li ◽  
...  
Keyword(s):  
Passive Control ◽  
Oscillation Amplitude ◽  
Rigid Wall ◽  
Wave Mode ◽  
Combustion Instabilities ◽  
Swirl Combustor ◽  
Acoustic Liners ◽  
Acoustic Liner ◽  
Bias Flow ◽  
Quarter Wave

Abstract Acoustic liner is one of effective passive control methods of combustion instabilities. This paper presents an experimental investigation about the suppression of the combustion instabilities using acoustic liners. A premixed swirling combustor was built and a specially designed acoustic liner was set at the downstream of the flame zone. Then, experiments of rigid wall, acoustic liner without and with tunable bias flow were carried out respectively. Furthermore, considering the viscous dissipation of airflow is temperature related, the temperature of the bias flow was adjusted in order to evaluate its effects on thermoacoustic instabilities. The bias flow was heated by electric taps before entering the acoustic liner in this rig. Results shows that the unstable Helmholtz mode could be triggered, and the oscillation amplitude grows with the increase of the bias flow Mach number, while the instability of 1/4 wavelength mode may be completely suppressed. Within the scope of the experiments, the unstable Helmholtz mode triggered by the bias flow can be attenuated by raising the bias flow temperature, while no substantial changes are observed about the quarter wave mode. These results are rarely reported in previous studies. Studying the effects of acoustic liner on combustion instabilities can provide useful knowledge regarding its application in real combustion systems.

scholarly journals Generation and Mitigation Mechanism Studies of Nonlinear Thermoacoustic Instability in a Modelled Swirling Combustor with a Heat Exchanger

Aerospace ◽  
2021 ◽  
Vol 8 (3) ◽  
pp. 60
Author(s):  
Yuze Sun ◽  
Dan Zhao ◽  
Xiaowei Zhu
Keyword(s):  
Heat Exchanger ◽  
Passive Control ◽  
Control Method ◽  
Dominant Frequency ◽  
Inlet Temperature ◽  
Swirl Combustor ◽  
Thermoacoustic Instability ◽  
Thermoacoustic Instabilities ◽  
Acoustic Fluctuations ◽  
Thermoacoustic Oscillations

In the present work, 3D Unsteady Reynolds-Averaged Navier-Stokes (URANS) simulations are performed to investigate the generation and mitigation mechanism of combustion-sustained thermoacoustic instabilities in a modelled swirl combustor. The effects of (1) swirling number SN, (2) inlet air flow rate Va and (3) inlet temperature Ti on the amplitudes and frequencies of swirling combustion-excited limit cycle oscillations are examined. It is found that the amplitude of acoustic fluctuations is increased with increasing SN and Va and decreased with the increase of Ti. The dominant frequency of oscillations is also found to increases with the increase of SN and Va. However, increasing Ti leads to the dominant frequency being decreased first and then increased. An alternative passive control method of installing an adjustable temperature heat exchanger on the combustion chamber wall is then proposed. Numerical results show that thermoacoustic oscillations could be excited and mitigated by setting the heat exchanger temperature to TH. Global and local Rayleigh indexes are applied to further reveal the excitation and attenuation effects on mechanisms. The present study is conducive to developing a simulation platform for thermoacoustic instabilities in swirling combustors. It also provides an alternative method to amplify or mitigate thermoacoustic oscillations.

Thermoacoustic Instabilities of Hydrogen-Enriched Partially Premixed Flames in a Swirl Combustor

2021 ◽  
Author(s):  
Y. Gong ◽  
D. Fredrich ◽  
A. J. Marquis ◽  
W. P. Jones ◽  
I. Boxx
Keyword(s):  
Field Method ◽  
The Self ◽  
Chamber Pressure ◽  
Stochastic Field ◽  
Cross Sectional ◽  
Swirl Combustor ◽  
Combustion Dynamics ◽  
Thermoacoustic Instabilities ◽  
Chemical Reaction Mechanism ◽  
Swirling Flames

Abstract Large eddy simulations (LES) of premixed hydrogen-enriched swirling flames were performed to investigate the flame topology and combustion instabilities with different hydrogen concentrations. A compressible LES approach is utilised to account for the self-excited combustion dynamics. A transported probability density function (pd f) approach is adopted to account for sub-grid scale (sgs) turbulence-chemistry interaction, and the solution to the joint sgs – pd f evolution equation of the scalars is obtained by the stochastic field method. The chemistry is represented using a reduced chemical reaction mechanism containing 15 reaction steps and 19 species. The results revealed that as the concentration of hydrogen increases, the flame is shortened in the injecting direction and more confined in the cross-sectional direction, which is consistent with experimental observations. The self-excited limit-cycle oscillations for all considered cases were successfully reproduced, with the predicted peak frequencies of the chamber pressure spectra in excellent agreement with the measured values. The feedback loop of the oscillations is successfully captured and analysed with the temporal evolution of axial velocity and heat release presented.

Suppression of Combustion Instabilities in a Premixed Swirl Combustor with Acoustic Liner

2019 ◽  
Author(s):  
Liangliang Xu ◽  
◽  
Guoqing Wang ◽  
Xunchen Liu ◽  
Lei Li ◽  
...  
Keyword(s):  
Combustion Instabilities ◽  
Swirl Combustor ◽  
Acoustic Liner ◽  
Suppression Of Combustion

Distributed Parameter Acoustic Modeling of a Perforation With Bias Flow

2011 ◽  
Author(s):  
Alireza Mazdeh ◽  
Reza Kashani
Keyword(s):  
Flow Characteristics ◽  
Distributed Parameter ◽  
Thermoacoustic Instabilities ◽  
Acoustic Liners ◽  
Current State ◽  
Large Eddy ◽  
Acoustic Liner ◽  
Bias Flow ◽  
Grazing Flow ◽  
Semi Empirical

Perforated acoustic liners (screech liners) with bias flow are commonly used for mitigation of thermoacoustic instabilities in augmentors. In addition to cooling the liner, the flow of air thru the liner perforation (dubbed ‘bias flow’) improves the damping effectiveness of the liner thru enhancing its energy dissipation. These liners are currently being designed using empirical design rules followed by build-test-improve steps, basically trial and error. The development of physics-based tools to assist in the design of such liners is of great interest to practitioners. In this paper, the existing work in developing analytical, semi-empirical, and numerical techniques such as Large-Eddy Simulations (LES) in exploring the damping effectiveness of an acoustic liner with bias flow are reviewed. The paper continues with presenting the research in progress that has been conducted by the authors in this area with the goal of expanding the numerical modeling work beyond the current state of the art by including the variables that were not incorporated in previous studies including, but not limited to, hole orientation, combined effect of tangential grazing flow and bias flow interaction with acoustics, and different flow characteristics (Mach and Reynolds number). In addition, the spatial distribution of pressure and velocity over the aperture area (instead of the current practice of averaging these variables) are being looked at.

Numerical Comparison of Drag Coefficient between Nacelle Lip-Skin with and without Bias Acoustic Liner

2016 ◽  
Vol 10 (6) ◽  
pp. 390 ◽  
Author(s):  
Qummare Azam ◽  
Mohd Azmi Ismail ◽  
Nurul Musfirah Mazlan ◽  
Musavir Bashir
Keyword(s):  
Drag Coefficient ◽  
Numerical Comparison ◽  
Acoustic Liner
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