Experimental and chemical kinetic study on the flame propagation characteristics of ammonia/hydrogen/air mixtures

Hydrogen-assisted oxidation of ammonia under flow reactor conditions was investigated through experiments and chemical kinetic modeling. Novel experiments, conducted in a tubular laminar flow reactor as a function of the NH 3 /H 2 ratio, stoichiometry, and temperature (725−1475 K), were analyzed along with literature results from tubular and jet-stirred flow reactors. Ignition and oxidation of NH 3 is strongly promoted by the presence of H 2 under all conditions investigated. In general, the behavior is captured well by the kinetic model. With an increasing fraction of H 2 in the fuel mixture, the generation of chain carriers gradually shifts from being controlled by the amine reaction subset to being dominated by the oxidation chemistry of H 2 , which is known more accurately. However, under reducing conditions, the H 2 consumption rate is strongly underpredicted. This shortcoming suggests that the thermochemistry of amine radicals and/or the formation of higher amines need further assessment. The present analysis shows that for lean oxidation of NH 3 /H 2 mixtures in tubular flow reactors, data obtained at higher temperatures, particularly for NO formation, may be strongly affected by the reaction during preheating or by mixing (dependent on reactor design) in the inlet section prior to the isothermal zone. Modeling predictions for the high pressure, medium-temperature ignition conditions in a large diesel engine indicate that NH 3 /H 2 fuel mixtures may still require a cofuel to secure stable ignition.

Section: Introductionmentioning

confidence: 99%

Flow Reactor Oxidation of Ammonia–Hydrogen Fuel Mixtures

Alzueta,

Mercader,

Cuoci

et al. 2024

“…Up to now, the combustion characteristics of ammonia-hydrogen-air mixtures have attracted much interest and been extensively studied by researchers, which have focused on different combustion parameters of ammonia-hydrogen-air mixtures such as laminar burning velocity, − NOx emissions, − and combustion limits. − Laminar burning velocity ( S l ) is an essential factor in laminar combustion, and S l of NH 3 /H 2 /air under various initial conditions has been experimentally investigated. , The results demonstrated that S l of NH 3 /H 2 /air increased with increasing hydrogen fractions and initial temperature but decreased as initial pressure was increased. S l of NH 3 /H 2 /air first increased and then decreased when the equivalence ratio was increased.…”

Section: Introductionmentioning

confidence: 99%

“…S l of NH 3 /H 2 /air premixed gases at high hydrogen addition ratios was enhanced because of chemical and transport effects resulting from the high reactivity and mobility of hydrogen . Apart from experimental measurements, some studies , have reported on the prediction of S l . Chen et al provided empirical formulas, which can predict S l of NH 3 /H 2 /air premixed gases well under various hydrogen addition ratios and equivalence ratios.…”

Section: Introductionmentioning

confidence: 99%

Experiments on the Vented Ammonia–Hydrogen–Air Deflagrations under Various Hydrogen Volume Fractions

Huang,

Guo,

Mei

et al. 2024

Although ammonia as a carbon-free fuel is regarded as an energy source worthy of significant development, how to address the shortcomings of its poor combustion properties has been a hot topic of research. Hydrogen enrichment is a promising solution to improve the combustion properties of ammonia, but at the same time, the potential explosion risk will inevitably be raised. In this paper, the effects of hydrogen volumetric fraction (χ) in NH 3 /H 2 on the NH 3 /H 2 /air deflagrations were experimentally investigated in a rectangular duct with an end-opening at an initial pressure and temperature of 101 kPa and 298 K, where χ was varied from 0.1 to 0.9. Results demonstrate that flame propagation and overpressure profiles inside and outside the chamber depend on χ. Buoyancy plays a significant role in flame propagation at χ = 0.1. More prominent deformation of the flame front propagating toward the closed end (CE) was observed in the experiments with higher χs. Helmholtz oscillations of the flame occurred in all tests, which resulted in pressure oscillations with a decreasing frequency as χ was increased. Acoustically enhanced combustion of NH 3 /H 2 /air remained at the CE, appeared when χ ≥ 0.7, and acoustic-type oscillations of the internal explosion overpressure and a pressure peak of p 2 formed in these tests. The amplitude of p 2 dropped as χ varied from 0.7 to 0.9. A proportional relationship between the highest explosion overpressure inside the chamber (p max ) and the square of the laminar burning velocity of NH 3 /H 2 /air (s l 2 ). When χ ≥ 0.3, a dominant pressure peak (p ext ) caused by the external explosion appeared in the external overpressure profiles, and its amplitude increased as χ varied from 0.3 to 0.9.

“…Energy is the basis for human survival and sustainable economic development . Coal is an extremely important energy source and is of great significance to the world economy.…”

Section: Introductionmentioning

confidence: 99%

“…Energy is the basis for human survival and sustainable economic development. 1 Coal is an extremely important energy source and is of great significance to the world economy. Gas, as an unconventional natural gas formed and adsorbed in coal seams during the process of coal formation, not only triggers disaster accidents but also is a type of clean energy.…”

Section: Introductionmentioning

confidence: 99%

Study on Multifractal of Coal Pore Structure Based on Low Pressure Argon Adsorption and Its Effect on Gas Adsorption/Desorption

Wang

Hao

et al. 2023

Although the coal pore structure is attracting the attention of researchers, studies on the multifractal and gas adsorption/desorption capacity are relatively few. In this study, multifractal characteristics were analyzed, and their effects on gas adsorption/desorption were discussed. The results showed that metamorphism and tectonism affected gas adsorption/desorption by changing the coal pore structure. The limit gas adsorption volume and initial desorption rate of tectonic coals increased by 3.9%–23.9% and 1.96–2.7 times, respectively. The information dimension (D 1), correlation dimension (D 2), and classical Hurst index gradually decreased with metamorphism and tectonism, while the Hausdorff dimension and Δα gradually increased, indicating that pore size distribution (PSD) was more decentralized or inhomogeneous. The evaluation results of the correlation between multifractal parameters and complexity confirmed its accuracy in assessing pore complexity. Multifractal parameters have a significant impact on gas adsorption/desorption capacity overall, mainly by reflecting the concentration degree, local density, and homogeneity of pores.