Experimental and numerical investigations on extinction strain rates in non-premixed counterflow methane and propane flames in an oxygen reduced environment

Eckart, Sven; Yu, Chunkan; Maas, Ulrich; Krause, Hartmut

doi:10.1016/j.fuel.2021.120781

Cited by 31 publications

(14 citation statements)

References 93 publications

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“…The production of OH correlates to extinction limits. 13,43,44 As discussed earlier in section 3.1, case E-F exhibited lower OH* chemiluminescence, i.e., a lower extinction limit than case E-C. Consistently, the simulation shows that case E-F produces less OH radical than case E-C, when considering the cumulative OH present in the domain.…”

Section: Defined Assupporting

confidence: 84%

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Effects of Ammonia Substitution in the Fuel Stream and Exhaust Gas Recirculation on Extinction Limits of Non-premixed Methane– and Ethylene–Air Counterflow Flames

Chu,

Scialabba,

Liu

et al. 2023

Energy Fuels

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The global extinction limits of non-premixed nitrogen/ammonia-substituted methane− and ethylene−air counterflow flames were experimentally evaluated. In comparison to nitrogen substitution, ammonia substitution reduced the extinction strain rates more. Measurements of OH* chemiluminescence, of which the intensity correlates with extinction limits, suggest that ammonia substitution reduces OH* production. The effects of transport, thermal and chemical properties on flame extinction of the ammonia-substituted flames were assessed, and it was found that their lower extinction limits were due to reactions that consume radicals, which hinder the chain-branching reactions. To mimic the effect of exhaust gas recirculation on the extinction limits of ammonia-substituted flames, carbon dioxide was added to the oxidizer stream. Lower extinction limits were observed with carbon dioxide addition as a result of thermal and chemical effects. Carbon dioxide addition lowered flame temperatures and, like ammonia substitution, introduced reactions that consume radicals. Nitric oxide (NO) production was quantitatively analyzed by simulations. It was found that, for ammonia flames, NO production was promoted by ammonia oxidation with OH, whereas for carbon dioxide addition, NO production was suppressed by the reduction of OH production.

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Section: Defined Assupporting

confidence: 84%

“…Fuels with higher reactivity, e.g., hydrogen, , have higher extinction limits compared to less reactive fuels, such as methane (CH 4 ) . From a modeling point of view, the measurements of extinction limits, expressed in the extinction strain rates, are often used for the validation of the chemical kinetic model. − …”

Section: Introductionmentioning

confidence: 99%

Effects of Ammonia Substitution in the Fuel Stream and Exhaust Gas Recirculation on Extinction Limits of Non-premixed Methane– and Ethylene–Air Counterflow Flames

Chu,

Scialabba,

Liu

et al. 2023

Energy Fuels

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“…At constant T ad , Da depends on the fuel–oxidizer composition, where Da decreases from cases 3–5 with the drop in OF and rise in Ø. The fact that case 5 has more fuel than case 3 increases the diffusion rate since the reaction mechanism of C 3 H 8 has numerous intermediate species 40 that enhance the diffusion rate, thus reducing the Da as Ø is increased at constant T ad . The change in flame thickness, on the other hand, shows an opposite behavior to the Da , as shown in Figure 12 b.…”

Section: Resultsmentioning

confidence: 99%

Analysis of Highly CO₂-Diluted Oxy-propane Flames Stabilized over a Multihole Burner of a Model Gas Turbine Combustor

et al. 2022

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Premixed oxy-propane flames are investigated numerically in a multihole model gas turbine combustor at various inlet mixture compositions over a range of equivalence ratios (Ø: 0.241−0.500), oxygen fractions (OF: 32.4−60.0%), and adiabatic flame temperatures (T ad : 1600−1900 K) at a constant bulk throat velocity of 5.2 m/s. The flames in multihole combustors are highly influenced by their corresponding adiabatic flame temperatures. Similar flame shapes are observed at constant T ad , where cases with (Ø = 0.241, OF = 60%) and (Ø = 0.50, OF = 32.4%) both represent lifted flames at T ad = 1600 K, anchored flames in (Ø = 0.276, OF = 60%) and (Ø = 0.50, OF = 36.6%) at T ad = 1750 K, and anchored stronger flames in cases (Ø = 0.313, OF = 60%), (Ø = 0.392, OF = 50%), and (Ø = 0.50, OF = 40.8%) at T ad = 1900 K. Flames in a multihole combustor are characterized by the presence of an outer recirculation zone (ORZ) only. In comparison with a swirlstabilized combustor in identical inlet conditions, flames in a multihole combustor demonstrate a lower Damkoḧler number (Da), higher flame thickness, elevated pattern factor, and increased CO emission. Due to the reduced vorticity level because of the absence of swirl motion, the multihole flames have higher axial temperature than the swirl-stabilized ones.

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“…On the basis of the boundary layer approximation (introduction of stream function) and introduction of two parameters, the tangential velocity gradient G and the tangential pressure gradient J , , the two-dimensional governing equations, which involve the continuity equation, Navier–Stokes equation, and conservation equation for the enthalpy and mass fractions of the chemical species in x and z coordinates, can be reduced to a set of equations in one-dimensional coordinate z . This two-parameter formulation is suitable for the description of stationary and unsteady flames and has been widely applied for different purposes, including steady and unsteady counterflow flames and predicting the extinction limit (see, e.g., refs − ). The corresponding mathematical equation system is expressed as ∂ ρ normalg ∂ t = prefix− 2 ρ normalg G − ∂ ( ρ g v z ) ∂ z ∂ G ∂ t = prefix− J ρ normalg − G 2 + 1 ρ normalg ∂ ∂ z ( η g ∂ G ∂ z ) − v z ∂ G ∂ z ∂ …”

Section: Modeling Of the Stagnation Flow Flame Coupled With The Plane...mentioning

confidence: 99%

Flame–Solid Interaction: Thermomechanical Analysis for a Steady Laminar Stagnation Flow Stoichiometric NH₃–H₂ Flame at a Plane Wall

Böhlke

Valera‐Medina

et al. 2023

Energy Fuels

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While thermomechanical analyses in solid and combustion processes in the gas phase are intensively studied separately, their interaction is less investigated. On one hand, the combustion system can be affected by the solid as a result of, for example, the heat conduction. On the other hand, the high-temperature flame can induce the thermal load in the solid, which significantly affects the mechanical stress field in the material. This work focuses on the coupling between the solid and flame and the combustion-induced mechanical stress in the material. The influence of the solid on the flame structures and properties and also the influence of the flame on the thermomechanical behavior in the solid are investigated. A stagnation flow NH 3 −H 2 −air flame to a plane wall is considered as a representative model, which is simple but also realistic in many engineering conditions. It is mainly found that an increase of the flame strain rate leads to an increase of thermomechanical stress in the wall, and the system pressure improves the flame stability against extinction but enlarges the induced thermomechanical stress at the same time. Furthermore, it is observed that the hydrogen content in the gas mixture does not affect the thermomechanical stress in the wall if the flames with different hydrogen additions are imposed with the same strain rate. On the basis of various flame parameters, it is also shown that the solid would also flow plastically under certain conditions, such as high pressures. From the viewpoint of the wall, it is mainly shown that the flame stability against extinction can be improved using wall materials with larger heat conductivities.

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Experimental and numerical investigations on extinction strain rates in non-premixed counterflow methane and propane flames in an oxygen reduced environment

Cited by 31 publications

References 93 publications

Effects of Ammonia Substitution in the Fuel Stream and Exhaust Gas Recirculation on Extinction Limits of Non-premixed Methane– and Ethylene–Air Counterflow Flames

Effects of Ammonia Substitution in the Fuel Stream and Exhaust Gas Recirculation on Extinction Limits of Non-premixed Methane– and Ethylene–Air Counterflow Flames

Analysis of Highly CO₂-Diluted Oxy-propane Flames Stabilized over a Multihole Burner of a Model Gas Turbine Combustor

Flame–Solid Interaction: Thermomechanical Analysis for a Steady Laminar Stagnation Flow Stoichiometric NH₃–H₂ Flame at a Plane Wall

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Experimental and numerical investigations on extinction strain rates in non-premixed counterflow methane and propane flames in an oxygen reduced environment

Cited by 31 publications

References 93 publications

Effects of Ammonia Substitution in the Fuel Stream and Exhaust Gas Recirculation on Extinction Limits of Non-premixed Methane– and Ethylene–Air Counterflow Flames

Effects of Ammonia Substitution in the Fuel Stream and Exhaust Gas Recirculation on Extinction Limits of Non-premixed Methane– and Ethylene–Air Counterflow Flames

Analysis of Highly CO2-Diluted Oxy-propane Flames Stabilized over a Multihole Burner of a Model Gas Turbine Combustor

Flame–Solid Interaction: Thermomechanical Analysis for a Steady Laminar Stagnation Flow Stoichiometric NH3–H2 Flame at a Plane Wall

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Analysis of Highly CO₂-Diluted Oxy-propane Flames Stabilized over a Multihole Burner of a Model Gas Turbine Combustor

Flame–Solid Interaction: Thermomechanical Analysis for a Steady Laminar Stagnation Flow Stoichiometric NH₃–H₂ Flame at a Plane Wall