Accurate Prediction of Confined Turbulent Boundary Layer Flashback Through a Critically Strained Flame Model

Novoselov, Alex G.; Ebi, Dominik; Noiray, Nicolas

doi:10.1115/1.4055413

Cited by 5 publications

(1 citation statement)

References 32 publications

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“…LES of boundary layer flashback in a confined channel were performed by Endres & Sattelmayer (2018, 2019) indicating that the pressure rise and adverse pressure gradient observed in boundary layer flashback cannot be simply derived by 1-D expressions. Finally, Novoselov, Ebi & Noiray (2022) has proposed a flashback model based on the extinction limits of strained flames. Despite the many above-mentioned studies, the underlying mechanism that controls the pressure increase and the formation of an adverse pressure gradient at the leading edge of flames undergoing boundary layer flashback remains elusive.…”

Section: Introductionmentioning

confidence: 99%

Study of flame–flow interactions in turbulent boundary layer premixed flame flashback over a flat plate using direct numerical simulation

Chen,

Wang,

Gruber

et al. 2023

J. Fluid Mech.

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Lean hydrogen/air premixed flame flashback in a turbulent boundary layer over a flat plate is investigated using three-dimensional direct numerical simulation with detailed chemical kinetics. The upstream propagation of the flame takes place in near-wall turbulence and the interaction between the flame and the approaching reactant flow is studied. It is found that backflow regions are always present immediately upstream of flame bulges that are convex towards the reactants, confirming earlier observations. A flashback speed, including the effects of flame displacement speed and flow velocity, is introduced to quantify the flame flashback behaviour. This analysis indicates that the flashback speed is overall positive and it is considerably affected by the presence of the backflow regions. A budget analysis of the pressure transport equation is performed to explain the presence of the backflow regions. It is suggested that the positive dilatation and thermal diffusion terms near the leading edge of flame bulges are the main reasons for the pressure increase, leading to an adverse pressure gradient. The effects of the flame-induced adverse pressure gradient on the structures of the turbulent boundary layer are also investigated. It is revealed that the near-wall mean velocity and skin-friction coefficient are reduced due to the adverse pressure gradient. The coherent vortical structures of the boundary layer turbulence are lifted by the adverse pressure gradient. The analysis of the Reynolds stress component showed that the ejection event is augmented by combustion while the sweep event is attenuated, which facilitates the occurrence of flame flashback.

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Section: Introductionmentioning

confidence: 99%

Study of flame–flow interactions in turbulent boundary layer premixed flame flashback over a flat plate using direct numerical simulation

Chen,

Wang,

Gruber

et al. 2023

J. Fluid Mech.

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Flame and flow dynamics during swirl flame flash-back

Yu,

Zhang,

Zhang

et al. 2024

Physics of Fluids

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Flash-back characteristics of lean-premixed syngas swirl flames were investigated using simultaneous OH planar laser-induced fluorescence and stereoscopic particle image velocimetry at a repetition rate of 10 kHz. The syngas consisted of carbon monoxide, carbon dioxide, and hydrogen. A stable burning condition was first reached. While keeping the flow rates of air and other fuel components fixed, the hydrogen flow rate was increased incrementally until the upstream-propagating flame suddenly flashed from the combustion chamber back into the plenum and quenched. There existed a condition at which appropriate changes in air/fuel flow rates could prevent the flame from irreversible flash-back; these conditions defined the recoverable operation limits. Spectral proper orthogonal decomposition results revealed a transition in flow characteristics from the precessing vortex core instability to Kelvin–Helmholtz (K–H) instability under recoverable conditions with increasing hydrogen, closely related to flow symmetry. A linear trend was observed between the bulk velocities under critical conditions and the corresponding laminar flame speeds, indicating a strong correlation between flow instability transition and flash-back limits.

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Thermoacoustic Characterization of a Premixed Multi Jet Burner for Hydrogen and Natural Gas Combustion

Beuth,

Reumschüssel,

von Saldern

et al. 2023

Journal of Engineering for Gas Turbines and Power

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In this study, the acoustics and flame dynamics of a prototype multi jet burner with 19 individual mixing tubes for operation with pure hydrogen and pure natural gas are experimentally investigated. The burner transfer matrix of the jet burner is determined from experimental data and acoustic network modeling, showing very good agreement. A comparison of the flame dynamics of the two fuels considering mass flow and equivalence ratio variation reveals that the flame transfer functions (FTFs) are dominated by a convective mechanism originating from the upstream end of the mixing tubes where the fuel is injected. Consequently, these are most likely fluctuations in the equivalence ratio that feature two characteristic time scales: the convection time in the mixing tubes and along the flame. The overall qualitative shape of the FTFs for hydrogen and natural gas at equal thermal power is found to be similar, with the dynamics of the natural gas flames being more responsive to acoustic excitation. Distinctly less pronounced phase decays are observed for hydrogen compared to natural gas operation. Moreover, the FTFs for H2 are found to change only slightly across the considered range of equivalence ratios. At the same time we observe only small changes in the corresponding static flame shapes. These observation are consistent with the hypothesis of a dominant convective mechanism. In conclusion, the study provides valuable information on the acoustics and flame dynamics of multi jet burners for flexible fuel operation.

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Accurate Prediction of Confined Turbulent Boundary Layer Flashback Through a Critically Strained Flame Model

Cited by 5 publications

References 32 publications

Study of flame–flow interactions in turbulent boundary layer premixed flame flashback over a flat plate using direct numerical simulation

Study of flame–flow interactions in turbulent boundary layer premixed flame flashback over a flat plate using direct numerical simulation

Flame and flow dynamics during swirl flame flash-back

Thermoacoustic Characterization of a Premixed Multi Jet Burner for Hydrogen and Natural Gas Combustion

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