Maximum stretched flame speeds of laminar premixed counter-flow flames at variable Lewis number

Salusbury, Sean D.; Bergthorson, Jeffrey M.

doi:10.1016/j.combustflame.2015.05.023

Cited by 25 publications

(10 citation statements)

References 53 publications

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“…One of such numbers is the Karlovitz number, Ka, which is an key parameter in the Borghi diagram [29]. The Ka is the ratio of chemical time scale and smallest turbulent time scale [30]. In this study, the combustion occurs in the wrinkled and corrugated flamelet regions.…”

Section: Resultsmentioning

confidence: 99%

Active-grid turbulence effect on the topology and the flame location of a lean premixed combustion

Alhumairi

Ertunç

2018

THERM SCI

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Lean premixed combustion under the influence of active-grid turbulence was computationally investigated, and the results were compared with experimental data. The experiments were carried out to generate a premixed flame at a thermal load of 9 kW from a single jet flow combustor. Turbulent combustion models, such as the coherent flame model and turbulent flame speed closure model were implemented for the simulations performed under different turbulent flow conditions, which were specified by the Reynolds number based on Taylor's microscale, the dissipation rate of turbulence, and turbulent kinetic energy. This study shows that the applied turbulent combustion models differently predict the flame topology and location. However, similar to the experiments, simulations with both models revealed that the flame moves toward the inlet when turbulence becomes strong at the inlet, that is, when Re λ at the inlet increases. The results indicated that the flame topology and location in the coherent flame model were more sensitive to turbulence than those in the turbulent flame speed closure model. The flame location behavior on the jet flow combustor significantly changed with the increase of Re λ .

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Section: Resultsmentioning

confidence: 99%

Active-grid turbulence effect on the topology and the flame location of a lean premixed combustion

Alhumairi

Ertunç

2018

THERM SCI

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“…Furthermore, the local extinction mechanism previously described implies that the relevant flame speed may be that of a highly strained premixed flame near extinction. For the mixtures considered in this work (i.e., lean hydrogen-air and lean methane-hydrogen-air mixtures) the effective Lewis number is sub-unity and therefore the flame speed increases with increasing strain rate [25,26]. This is illustrated in Fig.…”

Section: Location Of Leading Flame Propagationmentioning

confidence: 86%

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

Novoselov

Ebi

Noiray

2022

Journal of Engineering for Gas Turbines and Power

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A novel boundary layer flashback model is developed based on previous measurements that showed flashback limits may be related to strained premixed flame extinction. According to the model, flashback occurs at the equivalence ratio where the strained extinction limit flame speed matches the mean axial flow velocity one thermal distance from the wall. The model is validated by comparison with experimental measurements of flashback of confined non-swirling turbulent hydrogen-air flames. This comparison shows that the proposed model is capable of predicting confined turbulent boundary layer flashback across a large range of wall velocity gradients and preheat temperatures. The model is extended to methane-hydrogen-air flames in a swirling configuration using information about a single flashback event and shows good agreement with experimental measurements as a function of both hydrogen mole fraction in the fuel and pressure. In addition, inclusion of a mean non-reacting velocity field computed via Large Eddy Simulation allows for a significant increase in the accuracy of the model when applied to swirling flows. Ultimately, this model provides a new pathway for the design of flashback resistant gas turbines, even with the addition of fuels like hydrogen.

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“…Specifically, the strain rate at extinction was found to be constant for a given bulk inlet velocity regardless of the amount of hydrogen addition to the fuel. The implication of highly strained flames in the near-wall region is important for boundary layer flashback modeling because sub-unity Lewis number mixtures (including lean hydrogen-air, lean methane-air, and lean hydrogen-methane-air mixtures) all attain a maximum value of flame speed near the extinction limit [14,15]. This means that at a given thermochemical condition, flames will experience their highest flashback propensity near the extinction limit.…”

Section: Flashback Modelmentioning

confidence: 99%

The Effect of Hydrogen Addition on Confined Turbulent Boundary Layer Flashback Studied with a Critically Strained Flame Model

Novoselov

Ebi

Noiray

2022

AIAA SCITECH 2022 Forum

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The addition of hydrogen fuel to gas turbines otherwise operating on natural gas is a practical technique for the reduction of carbon emissions. However, hydrogen addition also modifies flame properties and leads to a significantly higher boundary layer flashback propensity. Robust methods to accurately predict these flashback limits are thus important to reducing emissions. In this work, a quantitative model for confined turbulent boundary layer flashback based on critically strained flames is presented. The model is based on the idea that strained flame extinction is directly responsible for controlling the flashback limit. The model predicts the occurrence of flashback when the one-dimensional strained flame speed at the extinction limit matches the axial flow velocity one thermal distance from the wall. The model agrees well with measurements of hydrogen-air flames in a non-swirling burner, and can be extended to methane-hydrogen-air flames in a swirling burner through minimal experimental data.

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Maximum stretched flame speeds of laminar premixed counter-flow flames at variable Lewis number

Cited by 25 publications

References 53 publications

Active-grid turbulence effect on the topology and the flame location of a lean premixed combustion

Active-grid turbulence effect on the topology and the flame location of a lean premixed combustion

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

The Effect of Hydrogen Addition on Confined Turbulent Boundary Layer Flashback Studied with a Critically Strained Flame Model

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