Simulating Bluff-Body Flameholders: On the Use of Proper Orthogonal Decomposition for Combustion Dynamics Validation

Contemporary tools for experimentation and computational modeling of unsteady and reacting flow open new opportunities for engineering insight into dynamic phenomena. In this article, we describe a novel use of proper orthogonal decomposition (POD) for validation of the unsteady heat release of a turbulent premixed flame stabilized by a vee-gutter bluff-body. Large-eddy simulations were conducted for the same geometry and flow conditions as examined in an experimental rig with chemiluminescence measurements obtained with a high-speed camera. In addition to comparing the experiment to the simulation using traditional time-averaging and pointwise statistical techniques, the dynamic modes of each are isolated using proper orthogonal decomposition (POD) and then compared mode-by-mode against each other. The results show good overall agreement between the shapes and magnitudes of the first modes of the measured and simulated data. A numerical study of into the effects of various simulation parameters on these heat release modes showed significant effects on the flame's effective angle but also on the size, shape, and symmetry patterns of the flame's dynamic modes.

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Temperature Ratio Effects on Bluff-Body Wake Dynamics Using Large Eddy Simulation and Proper Orthogonal Decomposition

Journal of Engineering for Gas Turbines and Power ◽

10.1115/1.4030383 ◽

2015 ◽

Vol 137 (12) ◽

Author(s):

Ryan Blanchard ◽

Wing Ng ◽

Uri Vandsburger

Keyword(s):

Large Eddy Simulation ◽

Heat Release ◽

Proper Orthogonal Decomposition ◽

Gas Turbines ◽

Bluff Body ◽

Orthogonal Decomposition ◽

Combustion Dynamics ◽

Eddy Simulation ◽

Large Eddy ◽

Proper Orthogonal

In this article, we describe the use of proper orthogonal decomposition (POD) to investigate how the dominant wake structures of a bluff-body-stabilized turbulent premixed flame are affected by the heat released by the flame itself. The investigation uses a validated large eddy simulation (LES) to simulate the dynamics of the bluff-body's wake (Blanchard et al., 2014, “Simulating Bluff-Body Flameholders: On the Use of Proper Orthogonal Decomposition for Wake Dynamics Validation,” ASME J. Eng. Gas Turbines Power, 136(12), p. 122603; Blanchard et al., 2014, “Simulating Bluff-Body Flameholders: On the Use of Proper Orthogonal Decomposition for Combustion Dynamics Validation,” ASME J. Eng. Gas Turbines Power, 136(12), p. 121504). The numerical simulations allow the effect of heat release, shown as the ratio of the burned to unburned temperatures, to be varied independently from the Damköhler number. Five simulations are reported with varying fractions of the heat release ranging from 0% to 100% of the value of the baseline experiment. The results indicate similar trends reported qualitatively by others, but by using POD to isolate the dominant heat release modes of each simulation, the decomposed data can clearly show how the previously reported flow structures transition from asymmetric shedding in the case of zero heat-release to a much weaker, but fully symmetric shedding mode in the case of full heat release with a much more elongated and stable wake.

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Advanced Identification of Coherent Structures in Swirl-Stabilized Combustors

Volume 4A: Combustion, Fuels and Emissions ◽

10.1115/gt2016-56591 ◽

2016 ◽

Author(s):

Moritz Sieber ◽

Christian Oliver Paschereit ◽

Kilian Oberleithner

Keyword(s):

Heat Release ◽

Proper Orthogonal Decomposition ◽

Coherent Structures ◽

High Speed ◽

Low Frequency ◽

Orthogonal Decomposition ◽

Time Resolved ◽

Operation Conditions ◽

Natural Dynamics ◽

Proper Orthogonal

We present an application of a newly introduced method to analyze the time-resolved experimental data from the flow field of a swirl-stabilized combustor. This method is based on classic proper orthogonal decomposition (POD) extended by a temporal constraint. The filter operation embedded in this method allows for continuous fading from the classic POD to the Fourier mode decomposition. This new method — called spectral proper orthogonal decomposition (SPOD) — allows for a clearer separation of the dominant mechanisms due to a clean spectral separation of phenomena. In this paper, the fundamentals of SPOD are shortly introduced. The actual focus is put on the application to a combustor flow. We analyze high-speed PIV measurements from flow fields in a combustor at different operation conditions. In these measurements, we consider externally actuated, as well as natural dynamics and reveal how the natural and actuated modes interact with each other. As shown in the paper, SPOD provides detailed insight into coherent structures in swirl flames. Two distinct PVC structures are found that are very differently affected by acoustic actuation. The coherent structures are related to heat release fluctuations, which are derived from simultaneously acquired OH* chemiluminescence measurements. Besides the actuated modes, a low frequency mode was found that significantly contribute to the global heat release fluctuations.

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Proper Orthogonal Decomposition Analysis of Non-Swirling Turbulent Stratified and Premixed Methane/Air Flames

Volume 4B: Combustion, Fuels and Emissions ◽

10.1115/gt2014-26222 ◽

2014 ◽

Author(s):

M. Mustafa Kamal ◽

Christophe Duwig ◽

Saravanan Balusamy ◽

Ruigang Zhou ◽

Simone Hochgreb

Keyword(s):

Flow Field ◽

Proper Orthogonal Decomposition ◽

High Speed ◽

Large Scale ◽

Bluff Body ◽

Decomposition Analysis ◽

Orthogonal Decomposition ◽

Stereoscopic Particle Image Velocimetry ◽

Large Scale Flow ◽

Proper Orthogonal

This paper reports proper orthogonal decomposition (POD) analyses for the velocity fields measured in a test burner. The Cambridge/Sandia Stratified Swirl Burner has been used in various studies as a benchmark for high resolution scalar and velocity measurements, for comparison with numerical model prediction. Flow field data was collected for a series of bluff-body stabilized premixed and stratified methane/air flames at turbulent, globally lean conditions (ϕ = 0.75) using high speed stereoscopic particle image velocimetry (HS-SPIV). In this paper, a modal analysis was performed to identify the large scale flow structures and their impact on the flame dynamics. The high speed PIV system was operated at 3 kHz to acquire a series of 4096 sequential flow field images both for reactive and non-reactive cases, sufficient to follow the large-scale spatial and temporal evolution of flame and flow dynamics. The POD analysis allows identification of vortical structures, created by the bluff body, and in the shear layers surrounding the stabilization point. In addition, the analysis reveals that dominant structures are a strong function of the mixture stratification in the flow field. The dominant energetic modes of reactive and non-reactive flows are very different, as the expansion of gases and the high temperatures alter the unstable modes and their survival in the flow.

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Advanced Identification of Coherent Structures in Swirl-Stabilized Combustors

Journal of Engineering for Gas Turbines and Power ◽

10.1115/1.4034261 ◽

2016 ◽

Vol 139 (2) ◽

Cited By ~ 16

Author(s):

Moritz Sieber ◽

Christian Oliver Paschereit ◽

Kilian Oberleithner

Keyword(s):

Heat Release ◽

Proper Orthogonal Decomposition ◽

Coherent Structures ◽

High Speed ◽

Low Frequency ◽

Orthogonal Decomposition ◽

Time Resolved ◽

Operation Conditions ◽

Natural Dynamics ◽

Proper Orthogonal

We present an application of a newly introduced method to analyze the time-resolved experimental data from the flow field of a swirl-stabilized combustor. This method is based on the classic proper orthogonal decomposition (POD) extended by a temporal constraint. The filter operation embedded in this method allows for continuous fading from the classic POD to the Fourier mode decomposition. This new method—called spectral proper orthogonal decomposition (SPOD)—allows for a clearer separation of the dominant mechanisms due to a clean spectral separation of phenomena. In this paper, the fundamentals of SPOD are shortly introduced. The actual focus is put on the application to a combustor flow. We analyze high-speed particle image velocimetry (PIV) measurements from flow fields in a combustor at different operation conditions. In these measurements, we consider externally actuated, as well as natural dynamics and reveal how the natural and actuated modes interact with each other. As shown in the paper, SPOD provides detailed insight into coherent structures in the swirl flames. Two distinct PVC structures are found that are very differently affected by acoustic actuation. The coherent structures are related to the heat release fluctuations, which are derived from simultaneously acquired OH* chemiluminescence measurements. Besides the actuated modes, a low frequency mode was found that significantly contribute to the global heat release fluctuations.

Download Full-text