Extinction limits and structure of counterflow nonpremixed methane-ammonia/air flames

Ku, Jae Won; Choi, Seok Keun; Kim, Hee Kyung; Lee, Seungro; Kwon, Oh Chae

doi:10.1016/j.energy.2018.09.113

Cited by 47 publications

(37 citation statements)

References 29 publications

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“…Up to date the corresponding characterization of such oxidative layers with sustainable energy carriers, such as ammonia or their blends, in innovative combustion regimes is still quite sparse. To the authors' best knowledge, until now very few papers dealt with this issue (Ku et al, 2018;Colson et al, 2020), despite they were focused more on the extinction characteristics of ammonia flames and their blends.…”

Section: Introductionmentioning

confidence: 99%

Reactive Structures of Ammonia MILD Combustion in Diffusion Ignition Processes

Sorrentino¹,

Sabia²,

Ariemma³

et al. 2021

Front. Energy Res.

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Reactive structures have been analyzed, when ammonia is used as a fuel, in a steady 1D counterflow diffusion flame layer, mimicking diffusion ignition processes. The characterization has been carried out in a wide range of feeding parameters under Moderate or Intense Low-oxygen Dilution (MILD) combustion conditions. Both the Hot-Fuel-Diluted-Fuel (HFDF) and Hot-Oxidant-Diluted-Fuel (HODF) configurations were studied to analyze the main effects of the inlet feeding conditions on the oxidative structures. The reaction zone has been analyzed in terms of temperature and heat release profiles in the mixture fraction space for various ranges of inlet parameters, using a standard code and a validated chemical kinetic scheme. Several features of the reaction zone have been recognized as reported also in previous works for hydrocarbon flames. They were used as discriminative for the achievement of various combustion regimes. In particular, the flame thickening process and the absence of correlation between the maximum heat release and the stoichiometric mixture fraction were analyzed to build maps of behaviors. The latter were reported on an inlet preheating level-temperature increase plane for fixed values of the bulk strain rate and system pressures. Another relevant feature previously reported with hydrocarbons in the literature, in Hot Diluted Diffusion Ignition (HDDI) processes under MILD conditions, was the pyrolysis depression. The latter characteristic has been not observed when ammonia is used as a fuel, for the operative conditions here investigated. Indeed, the heat release profiles do not show the presence of negative heat release regions. The results obtained for the HFDF configuration are strongly dependent on the system pressure level. Finally, the HODF condition has been also analyzed for ammonia at the atmospheric pressure. Boundaries of the combustion regimes and reactive structure features showed several differences between HFDF and HODF cases with respect to the inlet parameters.

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Section: Introductionmentioning

confidence: 99%

Reactive Structures of Ammonia MILD Combustion in Diffusion Ignition Processes

Sorrentino¹,

Sabia²,

Ariemma³

et al. 2021

Front. Energy Res.

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“…The addition of ordinary hydrocarbons as well as hydrogen is effective to improve flame stabilization and the gradual introduction of ammonia in existing large scale GTCC (gas turbine combined cycle) systems is possible. Most of the studies on ammonia/methane mixtures focused on small additions of NH3 to methane (CH4) flames with the reduction of NOx emissions as their purpose (Banna and Branch, 1981, Sullivan et al, 2002, Rahinov et al, 2006, Mendiara and Glarborg, 2009, Zieba et al, 2009, Barbas et al, 2013or Brackmann et al, 2018, while studies on larger quantities of NH3 remain limited to studies such as (Okafor et al, 2018, Ku et al, 2018. Thus, to develop efficient combustion systems for NH3/CH4 mixtures, fundamental flame characteristics and detailed chemistries should be carefully investigated.…”

Section: Introductionmentioning

confidence: 99%

“…However, when pressure rises, the extinction stretch rate increases significantly for NH3/air flames compared to CH4/air flames due to the differences in the effect of pressure on the major heat-releasing reactions of the chemical reaction paths of both flames (Colson et al, 2016). Studies on methane and hydrogen-doped ammonia nonpremixed counterflow flames were also performed by Choi et al (2015) and Ku et al (2018) showing large discrepancies between modeling and experimental data and the need for more detailed studies on those flames.…”

Section: Introductionmentioning

confidence: 99%

Experimental and Numerical Study of NH₃/CH₄ Counterflow Premixed and Non-premixed Flames for Various NH₃ Mixing Ratios

Colson

Hirano

Hayakawa

et al. 2020

Combustion Science and Technology

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Ammonia is a promising sustainable fuel, however, its low reactivity creates challenges in industrial applications. In this study, ammonia/methane mixtures were considered for premixed and non-premixed counterflow flames. The extinction stretch rate was measured over a wide range of ammonia/methane mixing ratios and compared to 1D numerical results from four different mechanisms. Additionally, for counterflow premixed twin flames, quantitative analysis based on the comparison of experimental and numerical FWHM of OH and NO profiles was performed. Results showed that in premixed flames, all the mechanisms investigated were inadequate for predicting the extinction stretch rate, specifically for lean flames. In non-premixed flames, Okafor's mechanism was accurately predicting the extinction stretch rate. For the FWHM analysis, the numerical mechanisms overpredicted both OH and NO apparition in the flame, except for Tian's mechanism which underpredicted OH apparition. GRI Mech 3.0 performed well for small quantities of ammonia but failed to reproduce the pure ammonia case.Okafor's and UCSD mechanisms gave better predictions of experimental trends, though overestimated both OH and NO apparition. In the FWHM analysis of both OH and NO, the lower R 2 values in the lean region suggest that the lean region should be the focus for mechanism improvement.

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“…By analyzing the ignition delay time and laminar flame structure, they found that harmful emissions can be significantly reduced. Ku et al [19] conducted experimental and computational studies on the basic combustion characteristics of methane-ammonia mixtures, developed a new reaction mechanism, and optimized it.…”

Section: Introductionmentioning

confidence: 99%

Research on Combustion Characteristics of Air–Light Hydrocarbon Mixing Gas

et al. 2020

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Air–light hydrocarbon mixing gas is a new type of city gas which is composed of light hydrocarbon with the main component of n-pentane and air mixed in a certain proportion. To explore the dominant reactions for CO production of air–light hydrocarbon mixing gas with different mixing degrees at the critical equivalence ratios, a computational study was conducted on the combustion characteristics, including the ignition delay time, laminar flame speed, extinction residence time, and emission of air–light hydrocarbon mixing gas at atmospheric pressure and room temperature in the present study. The calculated results indicate that the ignition delay time of air–light hydrocarbon mixing gas at temperatures of 1000–1118 K is greater than that of n-pentane, while the opposite at temperatures of 1118–1600 K. From the study of the laminar flame speed and ignition delay time, it was found that the essence of air–light hydrocarbon mixing gas is that its attribute parameter is determined by the ratio of n-pentane to the total amount of air at the moment of combustion. The changes in the extinction residence time and the CO emission index of air–light hydrocarbon mixing gas are not synchronized, that is the CO emission index is not necessarily small for air–light hydrocarbon mixing gas with excellent extinction residence time. CO sensitivity analysis and CO rate of production identified key species and reactions that are primarily responsible for CO formation and annihilation. The mixing degree plays a key role in the CO emission index of air–light hydrocarbon mixing gas, which has a constructive opinion on the future experiment and application of air–light hydrocarbon mixing gas.

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Extinction limits and structure of counterflow nonpremixed methane-ammonia/air flames

Cited by 47 publications

References 29 publications

Reactive Structures of Ammonia MILD Combustion in Diffusion Ignition Processes

Reactive Structures of Ammonia MILD Combustion in Diffusion Ignition Processes

Experimental and Numerical Study of NH₃/CH₄ Counterflow Premixed and Non-premixed Flames for Various NH₃ Mixing Ratios

Research on Combustion Characteristics of Air–Light Hydrocarbon Mixing Gas

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Extinction limits and structure of counterflow nonpremixed methane-ammonia/air flames

Cited by 47 publications

References 29 publications

Reactive Structures of Ammonia MILD Combustion in Diffusion Ignition Processes

Reactive Structures of Ammonia MILD Combustion in Diffusion Ignition Processes

Experimental and Numerical Study of NH3/CH4 Counterflow Premixed and Non-premixed Flames for Various NH3 Mixing Ratios

Research on Combustion Characteristics of Air–Light Hydrocarbon Mixing Gas

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Experimental and Numerical Study of NH₃/CH₄ Counterflow Premixed and Non-premixed Flames for Various NH₃ Mixing Ratios