Response of flames with different degrees of premixedness to acoustic oscillations

Kypraiou, Anna-Maria; Allison, Patton M.; Giusti, Andrea; Mastorakos, Epaminondas

doi:10.1080/00102202.2018.1452125

Cited by 16 publications

(16 citation statements)

References 27 publications

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“…It consists of a fuel pipe in the center and an outer section where from the bottom a co-flowing stream is provided through an inlet section with a cylindrical duct. Such a configuration has been used for instance in experimental [3] and numerical [1] investigations of the combustion process stability. Unlike in those works, in this paper, Figure 2 shows the computational domains and explains a two-part computational strategy.…”

Section: Computational Setupmentioning

confidence: 99%

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Numerical analysis of influence of various bluff-body shapes on diffusion flame dynamics

Kantoch

Wawrzak

Tyliszczak

2022

J. Phys.: Conf. Ser.

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In this paper, various bluff-body shapes (cylindrical, square, star) and two different surface topologies (smooth, wavy) are applied as passive tools for controlling a non-premixed hydrogen flame in a combustion chamber. We focus on the dynamics of the flame and its time-averaged characteristics in the close vicinity of an injection system within formed recirculation zones and also in a far-field. The research is performed with the help of large-eddy simulations (LES) method using the ANSYS Fluent software and a high-order academic code SAILOR. Flame behaviour is found to be strongly dependent on the geometry of the bluff-body whereas its wall topology affects the flame characteristics only slightly. In the cases with the square and star bluff-body, small vortical structures originating at the corners deform large vortical structures created by the Kelvin-Helmholtz instability mechanism. This intensifies the mixing and combustion process and, in the configuration with the square shape bluff-body, translates to the shortening of the recirculation zone by 15% of the equivalent bluff-body diameter and the flame, which in the axis develops closer to the bluff-body. The star shape leads to the most uniform flame at the radial border or the recirculation zone.

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Section: Computational Setupmentioning

confidence: 99%

“…They demonstrated that the combustion is most intense in the inner region of the recirculation zone. Both the passive and active control methods were applied jointly by Kypraiou et al [3] in a combustion chamber with an axial and radial injection system. The active control relied on the acoustic excitation of the oxidizer stream.…”

Section: Introductionmentioning

confidence: 99%

Numerical analysis of influence of various bluff-body shapes on diffusion flame dynamics

Kantoch

Wawrzak

Tyliszczak

2022

J. Phys.: Conf. Ser.

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“…The analysis of dissipation and dispersion of entropy and compositional blobs is a field where accurate numerical simulations can give further insight [152][153][154]. Limit cycles [155] as well as flame response to high-amplitude perturbations [71,156], typically characterized by a highly non-linear behaviour, are also important topics for the safe operation of modern engines and advanced numerical simulation can certainly contribute to the development of a better understanding and control of the phenomena [157].…”

Section: Examplesmentioning

confidence: 99%

Turbulent Combustion Modelling and Experiments: Recent Trends and Developments

Giusti

Mastorakos

2019

Flow Turbulence Combust

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The development of better laser-based experimental methods and the fast rise in computer power has created an unprecedented shift in turbulent combustion research. The range of species and quantities measured and the advent of kHz-level planar diagnostics are now providing great insights in important phenomena and applications such as local and global extinction, pollutants, and spray combustion that were hitherto unavailable. In simulations, the shift to LES allows better representation of the turbulent flow in complex geometries, but despite the fact that the grid size is smaller than in RANS, the push towards realistic conditions and the need to include more detailed chemistry that includes very fast species and thin reaction zones emphasize the necessity of a sub-grid turbulent combustion model. The paper discusses examples from current research with experiments and modelling that focus on flame transients (self-excited oscillations, local extinction), sprays, soot emissions, and on practical applications. These demonstrate how current models are being validated by experimental data and the concerted efforts the community is taking to promote the modelling tools to industry. In addition, the various coordinated International Workshops on non-premixed, premixed, and spray flames, and on soot are discussed and some of their target flames are explored. These comprise flames that are relatively simple to describe from a fluid mechanics perspective but contain difficult-to-model combustion problems such as extinction, pollutants and multi-mode reaction zones. Recently, swirl spray flames, which are more representative of industrial devices, have been added to the target flames. Typically, good agreement is found with LES and some combustion models such as the progress variable-mixture fraction flamelet model, the Conditional Moment Closure, and the Transported PDF method, but predicting soot emissions and the condition of complete extinction in complex geometries is still elusive.

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“…Similarly, POD has been extensively applied to various combustion problems, such as combustion dynamics, lean blowout, etc. [16][17][18].…”

Section: Introductionmentioning

confidence: 99%

Study of Dynamical Instabilities in Siemens Liquid Spray Injectors Using Complementary Modal Decomposition Techniques

Ajisafe

Talibi

Ducci

et al. 2019

Volume 4B: Combustion, Fuels, and Emissions

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Liquid fuel spray characterisation is essential for understanding the mechanisms underlying fuel energy release and pollutant formation. Careful selection of operating conditions can promote flow instabilities in the fuel spray which can enhance atomisation and fuel mixing, thereby resulting in more efficient combustion. However, the inherent instabilities present in the spray could have adverse effect on the combustor dynamics. Hence, it is important to better understand the dynamical behaviour of the spray, and particularly at representative operating conditions. This work describes an experimental investigation of dynamical behaviour of pressure-swirl atomisers used in Siemens industrial gas turbine combustors, at a range of chamber pressures and fuel injection pressures, using high speed laser planar imaging. Two modal decomposition techniques — Proper Orthogonal Decomposition (POD) and Dynamic Mode Decomposition (DMD) — are applied and compared to assess the spray dynamics. Results indicate that both POD and DMD are able to capture periodic structures occurring in the spray at different spatial length scales. The characteristic frequencies estimated from both the methods are in good agreement with each other. Both techniques are able to identify coherent structures with variable size, shape and level of staggering, which are observed to be dependent on the pressure difference across the atomiser and the chamber pressure. The spatio-temporally resolved data and the results could be used for spray model development and validation. Furthermore, the methods employed could be applied to other fuel atomisers, and more complicated conditions involving cross flow and higher chamber temperatures.

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Response of flames with different degrees of premixedness to acoustic oscillations

Cited by 16 publications

References 27 publications

Numerical analysis of influence of various bluff-body shapes on diffusion flame dynamics

Numerical analysis of influence of various bluff-body shapes on diffusion flame dynamics

Turbulent Combustion Modelling and Experiments: Recent Trends and Developments

Study of Dynamical Instabilities in Siemens Liquid Spray Injectors Using Complementary Modal Decomposition Techniques

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