LES flamelet modeling of hydrogen combustion considering preferential diffusion effect

Kai, Reo; Tokuoka, Taiki; Nagao, Jun; Pillai, Abhishek L.; Kurose, Ryoichi

doi:10.1016/j.ijhydene.2022.12.164

Cited by 19 publications

(5 citation statements)

References 67 publications

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“…LES coupled with the FGM combustion model was used to further investigate the cracked ammonia swirl flames. On the basis of our previous studies, ,− the LES–FGM method considered the non-unity Lewis numbers ( Le ), the NO transport equation, and the heat loss effect in this study. A series of laminar flamelets were calculated using the Chem1D software package .…”

Section: Methodologiesmentioning

confidence: 99%

Experimental and Numerical Investigation on Combustion Characteristics of Cracked Ammonia Flames

An,

Zhang,

Zhang

et al. 2024

Energy Fuels

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The combustion characteristics of cracked NH 3 flames are investigated experimentally and numerically. The one-dimensional (1D) calculations are performed to validate the accuracy of the reaction mechanisms in cracking conditions and to understand the fundamental characteristics of the cracked NH 3 flames. In the experiments, the local distributions of OH and NO and the species emissions of NO, NO 2 , N 2 O, and NH 3 are measured using hydroxyl radical planar laser-induced fluorescence (OH-PLIF), NO* chemiluminescence, and Fourier transform infrared (FTIR) spectroscopy, respectively. The effects of partial cracking on the flame structure and emission characteristics are investigated. In addition, the large eddy simulations (LESs) with flameletgenerated manifold (FGM) methods, which consider the preferential diffusion effect, are conducted to understand the validity of the LES and to further elucidate the effects of the cracking ratio (Cr) on cracked NH 3 flames. The 1D calculation results show that reaction mechanisms by Mei et al. (Mei, B.; Zhang, J.; Shi, X.; Xi, Z.; Li, Y. Enhancement of ammonia combustion with partial fuel cracking strategy: Laminar flame propagation and kinetic modeling investigation of NH 3 /H 2 /N 2 /air mixtures up to 10 atm. Combust.

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Section: Methodologiesmentioning

confidence: 99%

Experimental and Numerical Investigation on Combustion Characteristics of Cracked Ammonia Flames

An,

Zhang,

Zhang

et al. 2024

Energy Fuels

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“…( 5) is evaluated using the reaction rate obtained from the Flamelet-library, and the gas temperature is calculated from the enthalpy obtained by solving Eq.(3). Although the consideration of differential diffusion improves the accuracy of the FGM approach [23], the Lewis number is assumed to be unity, i.e., 𝐷 𝐷 𝜆 𝜌𝐶 ⁄ to focus on the heat loss effect. The FGM approach requires a database called the flamelet library, which is generated by the calculations of the onedimensional laminar premixed flames under various conditions.…”

Section: Flamelet-generated Manifold (Fgm) Approachmentioning

confidence: 99%

Prediction of boundary layer flashback limits of hydrogen flame using an LES/non-adiabatic FGM approach

Fukuba,

Nishiie,

Kai

et al. 2024

JGPP

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To design a low-emission hydrogen-fired gas turbine combustor, prevention of flashback is one of key issues. However, the detailed measurement of flashback is difficult and expensive, especially at the actual operation condition. Therefore, the high-precision numerical simulation technology is important to study the mechanism and countermeasures of flashback. In this study, a large eddy simulation (LES) using a non-adiabatic flamelet-generated manifold (NA-FGM) approach, considering the effects of heat loss, is applied to simulate hydrogen-air premixed flame propagating in a rectangular channel. Then, the validity of predicting flashback limits is examined. The results show that the NA-FGM approach quantitatively well captures the flashback limits variation observed in the experiments. This indicates that accounting for the influence of heat loss is crucial in achieving precise prediction of the flashback in developing a low-emission hydrogen gas turbine combustor. NOMENCLATURE𝐶 Progress variable [-] 𝐶 Isobaric specific heat [J/kg/K] 𝐷 Thermal diffusivity [m 2 /s] 𝐷 Diffusion coefficient 𝐷 𝐷 𝜆 𝜌𝐶 ⁄ [m 2 /s] ℎ Enthalpy of species 𝑘 [J/kg] 𝑗 Mass diffusion flux of species 𝑘 [kg/m 2 /s] 𝑚 Mass production rate of species 𝑘 [kg/m 3 /s] 𝑃 Pressure [Pa] 𝑞 SGS term of progress variable [kg/m 2 /s] 𝑞 SGS term of enthalpy [J/m 2 /s] 𝑞 SGS term of mixture fraction [kg/m 2 /s] 𝑞 Source term of heat loss [W/m 3 ] 𝑇 Temperature [K] 𝑢 Velocity vector [m/s] 𝑌 Mass fraction of species 𝑘 [-] 𝑍 Mixture fraction [-] 𝑈 Bulk flow velocity in rectangular channel [m/s] 𝑦 Separaiotn zone size [mm] 𝛿 Quenching distance [mm] Greeks 𝛼 Heat loss fraction 𝜆 Thermal conductivity [W/m/K]  Equivalence ratio [-] 𝜇 Viscosity [Pa•s] 𝜌 Density [kg/m 3 ] 𝜎 Shear stress tensor [Pa] 𝜏 SGS shear stress tensor [Pa] 𝜔 Generation rate of progress variable [1/s] 𝜔 Chemical reaction rate of species 𝑘 [1/s] Subscripts f Fuel k Chemical species st Stoichiometric air-to-fuel ratio m Premixed gas wall Wall

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“…As the governing equations, conservation equations of mass, momentum, enthalpy, and mass fractions of chemical species are solved with the equation of state for the ideal gas. The details can be found in the literature (Kai et al, 2023). For each diffusion model, the diffusion velocity is evaluated as mentioned in Section 2.…”

Section: Numerical Simulationmentioning

confidence: 99%

“…One-dimensional numerical simulations of unstretched premixed flames are performed using an in-house code named FK 3 (Kurose, 2023). This code has been employed in many researches on hydrogen combustions (e.g., Kai et al, 2020Kai et al, , 2023Shehab et al, 2022;Nagao et al, 2023).…”

Section: Numerical Simulationmentioning

confidence: 99%

A study on precise estimation of laminar burning velocity of lean hydrogen-air premixed flame (Effect of species diffusion models)

KAI,

WATANABE,

KUROSE

2024

Mechanical Engineering Journal

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Effects of species diffusion models on the laminar burning velocity 𝑆 𝐿 of lean hydrogen-air premixed flame are investigated by performing one-dimensional numerical simulations of lean hydrogen-air premixed flames at an equivalence ratio of 0.5. Maxwell-Stefan (MS) diffusion, mixture-averaged (MA) diffusion, and unity Lewis number diffusion are compared as the concentration diffusion models at a pressure of 0.1 MPa. Moreover, the contribution of the species thermal diffusion is also investigated under three different pressure (𝑃) and unburnt gas temperature (𝑇 𝑢 ) conditions. Results show that the MA diffusion well reproduces the results of MS diffusion including 𝑆 𝐿 while saving computational cost to three-fourths. The unity Lewis number diffusion overestimated 𝑆 𝐿 by 30 % because of the underestimation of the mass flux of H2. By considering the species thermal diffusion, 𝑆 𝐿 decreases by 6.4 % and 3.0 % under the reference (𝑃 = 0.1 MPa and 𝑇 𝑢 = 300 K) and HPT (𝑃 = 2 MPa and 𝑇 𝑢 = 673 K) conditions, respectively, and increases by 1.3 % under the HP condition (𝑃 = 2 MPa and 𝑇 𝑢 = 300 K). Under the reference and HPT conditions, the species thermal diffusion removes the H radical from the reactive region. This mitigates the chain-branching reaction of H + O2 → OH + O and decreases 𝑆 𝐿 . On the other hand, under the HP condition, the species thermal diffusion supplies the H radical toward the reactive region. This enhances the aforementioned chain-branching reaction and increases 𝑆 𝐿 . Under the HP condition, the recombination reaction of H + O2 + M → HO2 + M is enhanced by a high molar concentration of third body M because of high gas density. The large contribution of this reaction to the consumption of H radicals in the high-temperature region makes peak positions of mass fraction of H and mass flux of H by the species thermal diffusion lower temperature side, which leads to the supply of H radicals to the reactive region and the increase in 𝑆 𝐿 .

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LES flamelet modeling of hydrogen combustion considering preferential diffusion effect

Cited by 19 publications

References 67 publications

Experimental and Numerical Investigation on Combustion Characteristics of Cracked Ammonia Flames

Experimental and Numerical Investigation on Combustion Characteristics of Cracked Ammonia Flames

Prediction of boundary layer flashback limits of hydrogen flame using an LES/non-adiabatic FGM approach

A study on precise estimation of laminar burning velocity of lean hydrogen-air premixed flame (Effect of species diffusion models)

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