Auto-ignition kinetics of ammonia and ammonia/hydrogen mixtures at intermediate temperatures and high pressures

He, Xiaoyu; Shu, Bo; Nascimento, David; Moshammer, Kai; Costa, Mário; Fernandes, Ravi X.

doi:10.1016/j.combustflame.2019.04.050

Cited by 237 publications

(176 citation statements)

References 40 publications

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“…Such prediction results that ignition delay time increases exponentially with decreasing temperature under different pressure and equivalence ratio conditions are obtained based on the ignition chemistry of the chemical kinetics model. The calculated tendencies are consistent with previous literature simulation findings, for example, ignition studies of ammonia 29 and ammonia/hydrogen mixtures 31 …”

Section: Resultssupporting

confidence: 91%

“…For the different NH 3 /CH 4 fuel blends investigated, ignition delay time calculation results show exponential increase with decreasing temperature. The same as 60%NH 3 /40%CH 4 case analyzed in Section 4.1, such tendencies are obtained based on the chemical kinetics model, which are consistent with previous literature simulation findings of ammonia/hydrogen fuel blends 31 …”

Section: Resultssupporting

confidence: 89%

“…To promote the utilization of the ammonia/methane combustion, further studies are still needed to determine the fundamental combustion properties of ammonia‐based fuels. As an essential property of combustion, ignition characteristics studies on ammonia‐based fuels are still limited 29‐31 . Mathieu et al 29 performed ignition delay measurements of ammonia in shock tube under the pressures up to 30 atm and temperature of 1560 to 2455 K. A comprehensive kinetics model was also developed with satisfactory accuracy in prediction of ignition delay time and NOx emission of ammonia.…”

Section: Introductionmentioning

confidence: 99%

“…It was found that hydrogen concentration higher than 10% condition can have a significant promotion effect on the ignition delay times. He et al 31 investigated the kinetics of ammonia–hydrogen ignition using rapid compression machine experiments within the temperature range of 950 to 1150 K, pressure range of 20 to 60 bar and equivalence ratio range of 0.5 to 2. Effects of hydrogen addition and equivalence ratio were studied on the ignition delay properties.…”

Section: Introductionmentioning

confidence: 99%

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Experimental and modeling study on ignition delay of ammonia/methane fuels

et al. 2020

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Summary Ammonia mixed with methane is a potential clean fuel for engine applications toward a low carbon economy. Studies are scarce on ignition phenomenon for ammonia/methane fuels in literature. In the present study, the ignition characteristics for ammonia–methane–air mixtures have been investigated by both experimental measurements and numerical simulations. Ignition processes of a 60%ammonia/40%methane (mol%) fuel blend were investigated with shock‐tube experiments. Measurements of the ignition delay times were performed behind reflected shock waves for such fuel/air mixtures with different equivalence ratios of 0.5, 1, and 2, at pressures around 2 and 5 atm within the temperature range of 1369 to 1804 K. Experimental results were then compared with numerical prediction results employing detailed kinetic mechanism, which showed satisfactory agreement within most of the range of the temperatures, equivalence ratios, and pressures investigated. Within the temperature range of 1300 to 1900 K, pressure range of 1 to 10 atm, equivalence ratio range of 0.5 to 2, and methane proportion range of 0% to 50% in fuel blends, the impacts of temperature, pressure, equivalence ratio, and methane additive were simulated on the ignition delay times of the fuel blends based upon the numerical model. It was found that the improvement of ammonia/methane ignition is significant with the increase of temperature, pressure, and methane additive while it is relatively not sensitive to equivalence ratio within the studied conditions. This suggests a promising potential of such fuel blends in real engine application. In addition to the calculations, reaction sensitivity analyses were also performed to have a deep insight into the observed differences between ammonia/methane/air ignition delay times with variation of conditions.

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Section: Resultssupporting

confidence: 91%

Section: Resultssupporting

confidence: 89%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Experimental and modeling study on ignition delay of ammonia/methane fuels

et al. 2020

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“…A notable exception is Ref. [15], where the autoignition of NH 3 /H 2 /O 2 mixtures were studied and branching reactions were identified, to which the results were most sensitive. Several experimental studies point to the crucial importance of additives, which have so far been determined empirically, rather than algorithmically.…”

mentioning

confidence: 99%

Algorithmic Analysis of Chemical Dynamics of the Autoignition of NH3–H2O2/Air Mixtures

et al. 2019

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The dynamics of a homogeneous adiabatic autoignition of an ammonia/air mixture at constant volume was studied, using the algorithmic tools of Computational Singular Perturbation. Since ammonia combustion is characterized by both unrealistically long ignition delays and elevated NO x emissions, the time frame of action of the modes that are responsible for ignition was analyzed by calculating the developing time scales throughout the process and by studying their possible relation to NO x emissions. The reactions that support or oppose the explosive time scale were identified, along with the variables that are related the most to the dynamics that drive the system to an explosion. It is shown that reaction H 2 O 2 (+M) → OH + OH (+M) is the one contributing the most to the time scale that characterizes ignition and that its reactant H 2 O 2 is the species related the most to this time scale. These findings suggested that addition of H 2 O 2 in the initial mixture will influence strongly the evolution of the process. It was shown that ignition of pure ammonia advanced as a slow thermal explosion with very limited chemical runaway. The ignition delay could be reduced by more than two orders of magnitude through H 2 O 2 addition, which causes only a minor increase in NO x emissions.

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Effect of Intermediate Radicals on NO_x and De‐NO_x Characteristics of NH₃/H₂/Air Flames at High Pressure

et al. 2023

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The effect of NH, NH 2 , and HNO on NO x and De-NO x chemistry of a NH 3 /H 2 /air mixture at a pressure of 20 bar is investigated. Results suggest that the increase in pressure reduces NO x emissions and increases HO 2 radical production through the reaction H + O 2 (+M) HO 2 (+M). In contrast with OH and O radicals, the HO 2 radical is less reactive, which prevents NO formation. The fuelbound NO x emissions mainly depend on the reactions NH + OH NO + H, HNO(+M) NO + H(+M), HNO + OH NO + H 2 O, and HNO + O 2 NO + HO 2 , and thermal NO x depends on the reactions N + O 2 NO + N and N + OH NO + H. At a pressure of 20 bar, the N 2 O is further converted to NO 2 and N 2 through the reaction N 2 O + NO NO 2 + N 2 . The abundance of HO 2 radicals at high pressure also initiates the conversion of NO to NO 2 via the reaction NO + HO 2 NO 2 + H.

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Auto-ignition kinetics of ammonia and ammonia/hydrogen mixtures at intermediate temperatures and high pressures

Cited by 237 publications

References 40 publications

Experimental and modeling study on ignition delay of ammonia/methane fuels

Experimental and modeling study on ignition delay of ammonia/methane fuels

Algorithmic Analysis of Chemical Dynamics of the Autoignition of NH3–H2O2/Air Mixtures

Effect of Intermediate Radicals on NO_x and De‐NO_x Characteristics of NH₃/H₂/Air Flames at High Pressure

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Auto-ignition kinetics of ammonia and ammonia/hydrogen mixtures at intermediate temperatures and high pressures

Cited by 237 publications

References 40 publications

Experimental and modeling study on ignition delay of ammonia/methane fuels

Experimental and modeling study on ignition delay of ammonia/methane fuels

Algorithmic Analysis of Chemical Dynamics of the Autoignition of NH3–H2O2/Air Mixtures

Effect of Intermediate Radicals on NOx and De‐NOx Characteristics of NH3/H2/Air Flames at High Pressure

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Effect of Intermediate Radicals on NO_x and De‐NO_x Characteristics of NH₃/H₂/Air Flames at High Pressure