Approaches for Comparing Numerical Simulation of Combustion Instability and Flame Imaging

Hardi, Justin; Hallum, W. Zach; Huang, Cheng; Anderson, William E.

doi:10.2514/1.b35780

Cited by 23 publications

(6 citation statements)

References 44 publications

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“…DMD was applied to the high-speed flame radiation data in order to investigate the flame dynamics at the frequencies of interest. The DMD method has been used in past thermoacoustic instability research in order to extract the response of rocket combustor flames from visualisation data [3,14,16,29].…”

Section: Methodsmentioning

confidence: 99%

“…However, important research questions could not be answered by line-of-sight integrated 1D flame radiation measurements. In other experiments with less challenging environments than BKD, optical access has successfully been applied [13,14,21,23,29]. In these experiments, high-speed flame visualisation allowed further insight into the flame response to acoustic oscillations.…”

Section: Experimental Techniquementioning

confidence: 99%

See 1 more Smart Citation

Experimental Investigation of Injection-Coupled High-Frequency Combustion Instabilities

Armbruster¹,

Hardi²,

Oschwald³

2020

Notes on Numerical Fluid Mechanics and Multidisciplinary Design

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Self-excited high-frequency combustion instabilities were investigated in a 42-injector cryogenic rocket combustor under representative conditions. In previous research it was found that the instabilities are connected to acoustic resonance of the shear-coaxial injectors. In order to gain a better understanding of the flame dynamics during instabilities, an optical access window was realised in the research combustor. This allowed 2D visualisation of supercritical flame response to acoustics under conditions similar to those found in European launcher engines. Through the window, high-speed imaging of the flame was conducted. Dynamic Mode Decomposition was applied to analyse the flame dynamics at specific frequencies, and was able to isolate the flame response to injector or combustion chamber acoustic modes. The flame response at the eigenfrequencies of the oxygen injectors showed symmetric and longitudinal wave-like structures on the dense oxygen core. With the gained understanding of the BKD coupling mechanism it was possible to derive LOX injector geometry changes in order to reduce the risks of injection-coupled instabilities for future cryogenic rocket engines.

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Section: Methodsmentioning

confidence: 99%

Section: Experimental Techniquementioning

confidence: 99%

Experimental Investigation of Injection-Coupled High-Frequency Combustion Instabilities

Armbruster¹,

Hardi²,

Oschwald³

2020

Notes on Numerical Fluid Mechanics and Multidisciplinary Design

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“…For the propellant combination oxygen-hydrogen flame visualization is usually made with OH* chemiluminescence in the UV range at around 308 nm. High-speed flame radiation imaging has also widely been used to study acoustic-flame interaction in rocket engines [11,[19][20][21][22]. However, recent analysis of the flame emission spectra of hydrogenoxygen flames at different pressure levels by Fiala et al revealed some issues of OH* radiation at the extreme conditions of LPREs, as strong self-absorption and thermal excitation [23][24][25].…”

Section: Operating Conditionsmentioning

confidence: 99%

“…DMD as described by Schmid et al [27] enables the extraction of dominant periodically fluctuating phenomena at different frequencies. In the past, the DMD method has been used in thermoacoustic instability research in order to extract the distributed flame response at certain frequencies from flame visualization data [15,19,28,29].…”

Section: Dynamic Mode Decompositionmentioning

confidence: 99%

High-Speed Flame Radiation Imaging of Thermoacoustic Coupling in a High Pressure Research Thrust Chamber

Armbruster

Hardi

Suslov

et al. 2018

2018 Joint Propulsion Conference

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This work addresses the nature of supercritical hydrogen-oxygen flame coupling to acoustics through visualization under conditions representative of upper stage rocket engines. A research thrust chamber which shows self-excited combustion instabilities for certain operating conditions was used. Previous analysis proved that the instabilities are connected to injector acoustics. In this study a small optical access window was mounted in the chamber wall. High-speed flame radiation imaging of OH* and blue wavelengths has been applied in order to analyze the acoustic-flame interaction of one of the 42 flames. Dynamic mode decomposition results for a case with 80 bar chamber pressure showed that the flame dynamics are strongly influenced by the LOX injector acoustics, whereas for a 50 bar chamber pressure load point no flame response to injector acoustics was observed. A potential source of acoustic excitation for the oxygen injectors based on hydrodynamic effects is consistent with the contradictory behavior of the two load points.

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“…Sub-scale experiments can also be used to assess the thermoacoustic stability characteristics of a particular injector design. 20,21 Thermoacoustic instabilities are caused by the coupling of oscillating heat release rate ( q ˙ ′) with pressure oscillations ( p ′) in the combustion chamber. Instabilities can arise if the Rayleigh criterion is satisfied, which can be expressed as Measuring p ′ at the wall of a combustion chamber is relatively straight forward, whereas q ˙ ′ cannot be measured directly.…”

Section: Introductionmentioning

confidence: 99%

Flame dynamics of an injection element operated with LOX/H₂, LOX/CNG and LOX/LNG in a sub- and supercritical rocket combustor with large optical access

Martin

Armbruster

Stützer

et al. 2023

International Journal of Spray and Combustion Dynamics

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Hot fire tests were performed using a single-injector research combustor featuring a large optical access window ([Formula: see text] mm) for flame visualisation. Three test campaigns were conducted with the propellant combination of liquid oxygen and hydrogen, liquid oxygen and compressed-natural-gas, as well as liquid oxygen and liquefied-natural-gas at conditions relevant for main- and upper-stage rocket engines. The large optical access enabled synchronised flame imaging using ultraviolet and blue radiation wavelengths covering a large portion of the combustion chamber for various sets of sub- and supercritical operating conditions. Combined with temperature, pressure and unsteady pressure measurements, this data provides a high-quality basis for the validation of numerical modelling. Flame width, length and opening angle as features describing the flame topology were extracted from the imaging. The suitability of flame imaging using ultraviolet and blue radiation wavelengths as qualitative markers of heat release was evaluated. Two-dimensional distributions of the Rayleigh Index were calculated for intervals with and without high-amplitude, self-excited oscillations of the longitudinal acoustic resonance modes. The calculated Rayleigh Index values properly reflect the thermoacoustic state of the chamber, indicating that both types of imaging may be used for qualitative study of thermoacoustic coupling of high-pressure cryogenic flames.

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Approaches for Comparing Numerical Simulation of Combustion Instability and Flame Imaging

Cited by 23 publications

References 44 publications

Experimental Investigation of Injection-Coupled High-Frequency Combustion Instabilities

Experimental Investigation of Injection-Coupled High-Frequency Combustion Instabilities

High-Speed Flame Radiation Imaging of Thermoacoustic Coupling in a High Pressure Research Thrust Chamber

Flame dynamics of an injection element operated with LOX/H₂, LOX/CNG and LOX/LNG in a sub- and supercritical rocket combustor with large optical access

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Approaches for Comparing Numerical Simulation of Combustion Instability and Flame Imaging

Cited by 23 publications

References 44 publications

Experimental Investigation of Injection-Coupled High-Frequency Combustion Instabilities

Experimental Investigation of Injection-Coupled High-Frequency Combustion Instabilities

High-Speed Flame Radiation Imaging of Thermoacoustic Coupling in a High Pressure Research Thrust Chamber

Flame dynamics of an injection element operated with LOX/H2, LOX/CNG and LOX/LNG in a sub- and supercritical rocket combustor with large optical access

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Flame dynamics of an injection element operated with LOX/H₂, LOX/CNG and LOX/LNG in a sub- and supercritical rocket combustor with large optical access