Large Eddy Simulation of a turbulent lifted flame using multi-modal manifold-based models: Feasibility and interpretability

Novoselov, Alex G.; Lacey, Cristian E.; Perry, Barbara; Müeller, Michael E.

doi:10.1016/j.proci.2020.06.217

Cited by 6 publications

(2 citation statements)

References 22 publications

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“…Multiple studies have contributed to the problem of auto-ignition in hot turbulent environments in different configurations and with different fuels, e.g. [10,11,12,13,14]. The combustion behavior of hydrogen at auto-igniting conditions in a sequential combustor configuration has been experimentally investigated in our laboratory in [15].…”

Section: Introductionmentioning

confidence: 99%

Numerical study of ignition and combustion of hydrogen-enriched methane in a sequential combustor

Impagnatiello¹,

Malé²,

Noiray³

2022

Preprint

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Ignition and combustion behavior in the second stage of a sequential combustor are investigated numerically at atmospheric pressure for pure CH 4 fueling and for a CH 4 /H 2 fuel blend in 24:1 mass ratio using Large Eddy Simulation (LES). Pure CH 4 fueling results in a turbulent propagating flame anchored by the hot gas recirculation zone developed near the inlet of the sequential combustion chamber. Conversely, CH 4 /H 2 fueling results in a drastic change of the combustion process, with multiple auto-ignition kernels produced upstream of the main flame brush. Chemical Explosive Mode Analysis indicates that, when H 2 is added, flame stabilization in the combustion chamber is strongly supported by auto-ignition chemistry. The analysis of fuel decomposition pathways highlights that radicals advected from the first stage flame, in particular OH, induce a rapid fuel decomposition and cause the reactivity enhancement that leads to auto-ignition upstream of the sequential flame. This behavior is promoted by the relatively large mass fraction of OH radicals found in the flow reaching the second stage, which is approximately one order of magnitude greater than it would be at chemical equilibrium. The importance of the out-of-equilibrium vitiated air on the ignition behavior is proven via an additional LES that features weak auto-ignition kernel formation when equilibrium is artificially imposed. It is concluded, therefore, that parameters affecting the relaxation towards chemical equilibrium of the vitiated flow can have an important influence on the operability of sequential combustors fueled with varying fractions of H 2 blending.

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Section: Introductionmentioning

confidence: 99%

Numerical study of ignition and combustion of hydrogen-enriched methane in a sequential combustor

Impagnatiello¹,

Malé²,

Noiray³

2022

Preprint

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“…The primary issue is that manifolds are pre-generated by using an auxiliary system, such as counterflow or burner-stabilized laminar flames. It has been shown that the choice of the auxiliary system has a direct impact on the results [16][17][18][19][20] . Essentially, it is assumed that the flame structure is similar to that of the auxiliary system, which is difficult to ensure in complex flows.…”

Section: Introductionmentioning

confidence: 99%

Using approximate inertial manifold approach to model turbulent non-premixed combustion

Akram,

Raman

2021

Preprint

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The theory of inertial manifolds (IM) is used to develop reduced-order models of turbulent combustion. In this approach, the dynamics of the system are tracked in a low-dimensional manifold determined in-situ without invoking laminar flame structures or statistical assumptions about the underlying turbulent flow. The primary concept in approximate IM (AIM) is that slow dominant dynamical behavior of the system is confined to a low-dimension manifold, and fast dynamics respond to the dynamics on the IM instantaneously. Decomposition of slow/fast dynamics and formulation of an AIM is accomplished by only exploiting the governing equations.Direct numerical simulations (DNS) of initially non-premixed fuel-air mixtures developing in forced isotropic turbulence have been carried out to investigate the proposed model. Reaction rate parameters are varied to allow for varying levels of extinction and reignition. The AIM performance in capturing different flame behaviors is assessed both a priori and a posteriori. It is shown that AIM captures the dynamics of the flames including extinction and reignition. Moreover, AIM provides scalar dissipation rate, mixing time for reactive scalars, and closures for nonlinear terms without any additional modeling. The AIM formulation is found promising, and provides a new approach to modeling turbulent combustion.

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Numerical Study of Ignition and Combustion of Hydrogen-Enriched Methane in a Sequential Combustor

Impagnatiello,

Malé,

Noiray

2024

Flow Turbulence Combust

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Ignition and combustion behavior in the second stage of a sequential combustor are investigated numerically at atmospheric pressure for pure $${\text{CH}}_{4}$$ CH 4 fueling and for two $${\text{CH}}_{4}$$ CH 4 -$${\text{H}}_{2}$$ H 2 fuel blends in 24:1 and 49:1 mass ratios , respectively, using Large Eddy Simulation (LES). Pure $${\text{CH}}_{4}$$ CH 4 fueling results in a turbulent propagating flame anchored by the hot gas recirculation zones developed near the inlet of the sequential combustion chamber. As the $${\text{H}}_{2}$$ H 2 content increases, the combustion process changes drastically, with multiple auto-ignition kernels produced upstream of the main flame brush. Analysis of the explosive modes indicates that, for the highest $${\text{H}}_{2}$$ H 2 amount investigated, flame stabilization in the combustion chamber is strongly supported by auto-ignition chemistry. The analysis of fuel decomposition pathways highlights that radicals advected from the first stage flame, in particular OH, induce a rapid fuel decomposition and cause the reactivity enhancement that leads to auto-ignition upstream of the sequential flame. This behavior is promoted by the relatively large mass fraction of OH radicals found in the flow reaching the second stage, which is approximately one order of magnitude greater than it would be at chemical equilibrium. The importance of the out-of-equilibrium vitiated air on the ignition behavior is proven via an additional LES that features weak auto-ignition kernel formation when equilibrium is artificially imposed. It is therefore concluded that parameters affecting the relaxation towards chemical equilibrium of the vitiated flow can have an important influence on the operability of sequential combustors fueled with varying fractions of $${\text{H}}_{2}$$ H 2 blending.

show abstract

Large Eddy Simulation of a turbulent lifted flame using multi-modal manifold-based models: Feasibility and interpretability

Cited by 6 publications

References 22 publications

Numerical study of ignition and combustion of hydrogen-enriched methane in a sequential combustor

Numerical study of ignition and combustion of hydrogen-enriched methane in a sequential combustor

Using approximate inertial manifold approach to model turbulent non-premixed combustion

Numerical Study of Ignition and Combustion of Hydrogen-Enriched Methane in a Sequential Combustor

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