Acoustic Analysis of a Liquid Fuel Swirl Combustor Using Dynamic Mode Decomposition

2015 ◽  
Author(s):  
Abdulla Ghani ◽  
Laurent Gicquel ◽  
Thierry Poinsot
Keyword(s):  
Acoustic Analysis ◽  
Dynamic Mode Decomposition ◽  
Dynamic Mode ◽  
Mean Flow ◽  
Swirl Combustor ◽  
Eddy Simulation ◽  
Mode Decomposition ◽  
Flame Response ◽  
Unstable Combustion ◽  
Flow Effects

The flame transfer function (FTF) of an aeronautical burner in a rectangular combustion chamber is determined using large eddy simulation (LES). The configuration contains an industrial swirling device placed in a laboratory combustor. The swirler comprises three air passages and liquid kerosene is injected through a pilot and a multipoint injection device including 24 injection holes. In order to reduce computational costs, the forcing process for FTF determination is limited to three forcing cycles. Application of the dynamic mode decomposition (DMD) allows to extract the coherent flow structures at the forcing frequency and to construct local flame response and time delay fields. In a next step, modal analysis is carried out with a Helmholtz solver where acoustic boundary conditions are utilized taking mean flow effects into account. The latter allows to model mean flow effects in a zero Mach number framework. Results are compared with experimental observations: stable and unstable combustion modes for different outlet impedances are correctly identified by this methodology. All results are validated against experimental data and show good agreement.

scholarly journals Analysis of V-Gutter Reacting Flow Dynamics Using Proper Orthogonal and Dynamic Mode Decompositions

Energies ◽  
2020 ◽  
Vol 13 (18) ◽  
pp. 4886 ◽  
Author(s):  
Yang Yang ◽  
Xiao Liu ◽  
Zhihao Zhang
Keyword(s):  
Shear Layer ◽  
Large Scale ◽  
Dynamic Mode Decomposition ◽  
Dynamic Mode ◽  
Reacting Flow ◽  
Eddy Simulation ◽  
Mode Decomposition ◽  
Wake Instability ◽  
Shedding Frequency ◽  
Proper Orthogonal

The current work is focused on investigating the potential of data-driven post-processing techniques, including proper orthogonal decomposition (POD) and dynamic mode decomposition (DMD) for flame dynamics. Large-eddy simulation (LES) of a V-gutter premixed flame was performed with two Reynolds numbers. The flame transfer function (FTF) was calculated. The POD and DMD were used for the analysis of the flame structures, wake shedding frequency, etc. The results acquired by different methods were also compared. The FTF results indicate that the flames have proportional, inertial, and delay components. The POD method could capture the shedding wake motion and shear layer motion. The excited DMD modes corresponded to the shear layer flames’ swing and convect motions in certain directions. Both POD and DMD could help to identify the wake shedding frequency. However, this large-scale flame oscillation is not presented in the FTF results. The negative growth rates of the decomposed mode confirm that the shear layer stabilized flame was more stable than the flame possessing a wake instability. The corresponding combustor design could be guided by the above results.

A Flow Dynamic Characteristic Analysis of A Single Radial Swirler Combustor

2019 ◽  
Vol 0 (0) ◽  
Author(s):  
Kyobin Lee ◽  
Jong-Chan Kim ◽  
Hong-Gye Sung
Keyword(s):  
Helmholtz Resonator ◽  
Dynamic Structure ◽  
Dynamic Mode Decomposition ◽  
Dynamic Mode ◽  
Fuel Injector ◽  
Characteristic Analysis ◽  
Flow Dynamic ◽  
Eddy Simulation ◽  
Mode Decomposition ◽  
German Aerospace

Abstract A diffusion combustor with a single radial swirler in non-reacting condition is investigated via a large eddy simulation (LES). Three dynamic analysis methods – the fast Fourier transform (FFT), proper orthogonal decomposition (POD) and dynamic mode decomposition (DMD) – are implemented to investigate the flow dynamic characteristics of the combustor. The kerosene-air combustor analyzed in the study was designed by the German Aerospace Center (DLR). It has a square cross-section and uses kerosene as fuel, which is modeled as a pre-vaporized and surrogated fuel consisting of 242 species. The first tangential(1T) mode in combustor caused by the swirler emerges dominantly in the combustor. This 1T mode exhibits the largest amount energy in the combustor dynamics, as verified by POD, and the DMD analysis determines the frequency of 1876.8 Hz. The fuel injector dynamics is associated with Helmholtz resonator frequency of 816.5 Hz. To analyze the instability, the DMD method is employed to investigate the growth rate of the most dominant dynamic structure.

Unravelling the large-scale circulation modes in turbulent Rayleigh–Bénard convection

2021 ◽  
Author(s):  
Susanne Horn ◽  
Peter J. Schmid ◽  
Jonathan M. Aurnou
Keyword(s):  
Large Scale ◽  
Three Dimensional ◽  
Dynamic Mode Decomposition ◽  
Dynamic Mode ◽  
Mean Flow ◽  
Large Scale Circulation ◽  
Convective Systems ◽  
Aspect Ratios ◽  
Mode Decomposition ◽  
Coherent Flow Structure

Abstract The large-scale circulation (LSC) is the most fundamental turbulent coherent flow structure in Rayleigh-B\'enard convection. Further, LSCs provide the foundation upon which superstructures, the largest observable features in convective systems, are formed. In confined cylindrical geometries with diameter-to-height aspect ratios of Γ ≅ 1, LSC dynamics are known to be governed by a quasi-two-dimensional, coupled horizontal sloshing and torsional (ST) oscillatory mode. In contrast, in Γ ≥ √2 cylinders, a three-dimensional jump rope vortex (JRV) motion dominates the LSC dynamics. Here, we use dynamic mode decomposition (DMD) on direct numerical simulation data of liquid metal to show that both types of modes co-exist in Γ = 1 and Γ = 2 cylinders but with opposite dynamical importance. Furthermore, with this analysis, we demonstrate that ST oscillations originate from a tilted elliptical mean flow superposed with a symmetric higher order mode, which is connected to the four rolls in the plane perpendicular to the LSC in Γ = 1 tanks.

Mixed Acoustic-Entropy Combustion Instabilities in a Model Aeronautical Combustor: Large Eddy Simulation and Reduced Order Modeling

2017 ◽  
Vol 140 (3) ◽  
Author(s):  
Florent Lacombe ◽  
Yoann Méry
Keyword(s):  
Large Eddy Simulation ◽  
Diffusion Flame ◽  
Combustion Process ◽  
Premixed Flame ◽  
Dynamic Mode Decomposition ◽  
Dynamic Mode ◽  
Combustion Instabilities ◽  
Eddy Simulation ◽  
Mode Decomposition ◽  
Large Eddy

This article focuses on combustion instabilities (CI) driven by entropy fluctuations which is of great importance in practical devices. A simplified geometry is introduced. It keeps the essential features of an aeronautical combustion chamber (swirler, dilution holes, and outlet nozzle), while it is simplified sufficiently to ease the analysis (rectangular vane, one row of holes of the same diameter, no diffuser at the inlet of the chamber, and circular nozzle at the outlet). A large eddy simulation (LES) is carried out on this geometry and the limit cycle of a strong CI involving the convection of an entropy spot is obtained. The behavior of the instability is analyzed using phenomenological description and classical signal analysis. One shows that the system can be better described by considering two reacting zones: a rich mainly premixed flame is located downstream of the swirler and an overall lean diffusion flame is stabilized next to the dilution holes. In a second step, dynamic mode decomposition (DMD) is used to visualize, analyze, and model the complex phasing between different processes affecting the reacting zones. Using these data, a zero-dimensional (0D) modeling of the premixed flame and of the diffusion flame is proposed. These models provide an extended understanding of the combustion process in an aeronautical combustor and could be used or adapted to address mixed acoustic-entropy CI in an acoustic code.

A comparative study of DES type methods for mild flow separation prediction on a NACA0015 airfoil

2017 ◽  
Vol 27 (11) ◽  
pp. 2528-2543 ◽  
Author(s):  
Liang Wang ◽  
Liying Li ◽  
Song Fu
Keyword(s):  
Separated Flow ◽  
Dynamic Mode Decomposition ◽  
Dynamic Mode ◽  
Detached Eddy Simulation ◽  
Reynolds Stresses ◽  
Content Type ◽  
Eddy Simulation ◽  
Mode Decomposition ◽  
Flow Phenomena ◽  
Critical Dynamic

Purpose The purpose of this paper is to numerically investigate the mildly separated flow phenomena on a near-stall NACA0015 airfoil, by using Detached-Eddy Simulation (DES) type methods. It includes a comparison of different choices of underlying Reynolds-averaged Navier–Stokes model as well as subgrid-scale stress model in Large-Eddy simulation mode. Design/methodology/approach The unsteady flow phenomena are simulated by using delayed DES (DDES) and improved DDES (IDDES) methods, with an in-house computational fluid dynamics solver. Characteristic frequencies in different flow regions are extracted using fast Fourier transform. Dynamic mode decomposition (DMD) method is applied to uncover the critical dynamic modes. Findings Among all the DES type methods investigated in this paper, only the Spalart–Allmaras-based IDDES captures the separation point as measured in the experiments. The classical vortex-shedding and the shear-layer flapping modes for airfoil flows with shallow separation are also found from the IDDES results by using DMD. Originality/value The value of this paper lies in the assessment of five different DES-type models through the detailed investigation of the Reynolds stresses as well as the separation and reattachment.

Global Stability Analysis of an Academic Rotor/Stator Cavity Subject to Periodic and Simple Wall Oscillations

2021 ◽  
Author(s):  
Mark Noun ◽  
Laurent Gicquel ◽  
Gabriel Staffelbach
Keyword(s):  
Stability Analysis ◽  
Global Stability ◽  
Pressure Fluctuations ◽  
Dynamic Mode Decomposition ◽  
Forced Flow ◽  
Dynamic Mode ◽  
Global Stability Analysis ◽  
Eddy Simulation ◽  
Mode Decomposition ◽  
Spatio Temporal

Abstract Complex unsteady phenomena can appear in turbomachinery components and result in the self-sustained oscillatory motion of the fluid as found in aeronautical engines or rocket turbopumps for example. The origin of these oscillations often results from the complex coupling between flow non linearities and structure motion generating major risks for the operation of the engine and even undermining its components. For instance, in turbines, the internal components that are most liable to vibrate are the blades and discs. In this context, it is critical to understand the effect of the vibrating components on the flow stability in rotor/stator cavities. In order to address this problem, an academic rotor/stator cavity subject to periodic wall oscillations is investigated in the current paper where the frequency of the vibrations are imposed and correspond to the previously identified unstable fluid modes inside the cavity. The objective is to understand the behavior of the flow when subject to a periodic forcing imposed by the rotor motion. To do so, predictive numerical strategies are established based on Large Eddy Simulation (LES) in conjunction to a global stability analysis which seem to be a promising method to capture flow instabilities. Focus is here brought to the underlying pressure fluctuations found inside the cavity using spectral analysis complemented with the global stability analysis, demonstrating that such tools can address forced flow problems. More specifically and for all simulations, the results of the global stability analysis are compared to a Dynamic Mode Decomposition (DMD) of LES predictions by reconstructing the corresponding modes through a spatio-temporal approach showing that the new fluid limit cycles present modes that shift or completely disappear compared to the unforced case, the forcing mechanism altering the stability of the entire system.

scholarly journals Analysis and Modelling of Entropy Modes in a Realistic Aeronautical Gas Turbine

2013 ◽  
Author(s):  
Emmanuel Motheau ◽  
Franck Nicoud ◽  
Yoann Mery ◽  
Thierry Poinsot
Keyword(s):  
Transfer Functions ◽  
Acoustic Mode ◽  
Dynamic Mode Decomposition ◽  
Dynamic Mode ◽  
Acoustic Coupling ◽  
Eddy Simulation ◽  
Mode Decomposition ◽  
Exit Nozzle ◽  
Large Eddy ◽  
Aero Engines

A combustion instability in a combustor typical of aero-engines is analyzed and modeled thanks to a low order Helmholtz solver. A Dynamic Mode Decomposition (DMD) is first applied to the Large Eddy Simulation (LES) database. The mode with the highest amplitude shares the same frequency of oscillation as the experiment (approx. 350 Hz) and it shows the presence of large entropy spots generated within the combustion chamber and convected down to the exit nozzle. The lowest purely acoustic mode being in the range 650–700 Hz, it is postulated that the instability observed around 350 Hz stems from a mixed entropy/acoustic mode where the acoustic generation associated with the entropy spots being convected throughout the choked nozzle plays a key role. A Delayed Entropy Coupled Boundary Condition is then derived in order to account for this interaction in the framework of a Helmholtz solver where the baseline flow is assumed at rest. When fed with appropriate transfer functions to model the entropy generation and convection from the flame to the exit, the Helmholtz solver proves able to predict the presence of an unstable mode around 350 Hz, in agreement with both the LES and the experiments. This finding supports the idea that the instability observed in the combustor is indeed driven by the entropy/acoustic coupling.

Mixed Acoustic-Entropy Combustion Instabilities in a Model Aeronautical Combustor: Large Eddy Simulation and Reduced Order Modeling

2017 ◽  
Author(s):  
Florent Lacombe ◽  
Yoann Mery
Keyword(s):  
Large Eddy Simulation ◽  
Diffusion Flame ◽  
Combustion Process ◽  
Premixed Flame ◽  
Dynamic Mode Decomposition ◽  
Dynamic Mode ◽  
Combustion Instabilities ◽  
Eddy Simulation ◽  
Mode Decomposition ◽  
Large Eddy

This article focuses on Combustion Instabilities (CI) driven by entropy fluctuations which is of great importance in practical devices. A simplified geometry is introduced. It keeps the essential features of an aeronautical combustion chamber (swirler, dilution holes, outlet nozzle) while it is simplified sufficiently to ease the analysis (rectangular vane, one row of holes of the same diameter, no diffuser at the inlet of the chamber, circular nozzle at the outlet). A Large Eddy Simulation (LES) is carried out on this geometry and the limit cycle of a strong CI involving the convection of an entropy spot is obtained. The behavior of the instability is analyzed using phenomenological description and classical signal analysis. One shows that the system can be better described by considering two reacting zones: a rich mainly premixed flame is located downstream of the swirler and an overall lean diffusion flame is stabilized next to the dilution holes. In a second step, Dynamic Mode Decomposition (DMD) is used to visualize, analyze and model the complex phasing between the different processes affecting the reacting zones. Using these data, a 0D modeling of the premixed flame and of the diffusion flame is proposed. These models provides an extended understanding of the combustion process in an aeronautical combustor and could be used or adapted to address mixed acoustic-entropy CI in an acoustic code.

scholarly journals Large Eddy Simulation and Dynamic Mode Decomposition of Turbulent Mixing Layers

2021 ◽  
Vol 11 (24) ◽  
pp. 12127
Author(s):  
Yuwei Cheng ◽  
Qian Chen
Keyword(s):  
Large Eddy Simulation ◽  
Turbulent Mixing ◽  
Mixing Layer ◽  
Mixing Layers ◽  
Dynamic Mode Decomposition ◽  
Dynamic Mode ◽  
Random Disturbance ◽  
Eddy Simulation ◽  
Mode Decomposition ◽  
Large Eddy

Turbulent mixing layers are canonical flow in nature and engineering, and deserve comprehensive studies under various conditions using different methods. In this paper, turbulent mixing layers are investigated using large eddy simulation and dynamic mode decomposition. The accuracy of the computations is verified and validated. Standard dynamic mode decomposition is utilized to flow decomposition, reconstruction and prediction. It was found that the dominant-mode selection criterion based on mode amplitude is more suitable for turbulent mixing layer flow compared with the other three criteria based on singular value, modal energy and integral modal amplitude, respectively. For the mixing layer with random disturbance, the standard dynamic mode decomposition method could accurately reconstruct and predict the region before instability happens, but is not qualified in the regions after that, which implies that improved dynamic mode decomposition methods need to be utilized or developed for the future dynamic mode decomposition of turbulent mixing layers.

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