A chemical kinetic analysis: Influence of post-flame chemistry, combustion pressure, premixing degree (fully premixed to non-premixed), and secondary air supply on NOx emissions from NH3/CH4-air combustion

Article Thermodynamics

Experimental study and numerical validation of oxy-ammonia combustion at elevated temperatures and pressures

Alka Karan et al.

Summary: The study focuses on testing laminar flame speed data for ammonia combustion at elevated conditions, with a literature review and sensitivity analysis conducted.

COMBUSTION AND FLAME (2022)

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Article Energy & Fuels

Reducing NOx Emission of Swirl-Stabilized Ammonia/Methane Tubular Flames through a Fuel-Oxidizer Mixing Strategy

Yuanping Yang et al.

Summary: This study investigated the impact of various fuel-oxidizer mixing strategies on the NOx performance of ammonia, proposing a new ammonia co-combustion technology and demonstrating the role of NH2 radicals in reducing NOx emissions.

ENERGY & FUELS (2022)

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Article Energy & Fuels

Chemical kinetic analysis on influence of hydrogen enrichment on the combustion characteristics of ammonia air using newly proposed reaction model

Anand Shankar Singh et al.

Summary: Ammonia has shown potential as a green fuel, and blending it with hydrogen can overcome challenges in combustion. A new reaction model for NH3/H-2/air mixtures with 32 species and 259 reactions closely follows experimental trends. Hydrogen enrichment improves heat release rate and flame speed of ammonia, making it a promising industrial fuel.

INTERNATIONAL JOURNAL OF ENERGY RESEARCH (2022)

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Article Chemistry, Physical

Effects of inter-stage mixing on the NOx emission of staged ammonia combustion

Zhaoxing Li et al.

Summary: This paper presents a modeling study on the effects of inter-stage mixing on the NOx emission of NH3 fueled rich-lean staged combustion. The study reveals that the quality of the inter-stage mixing has a significant impact on NOx emission, with poor mixing leading to increased NOx. However, at higher values of the mixing ratio, poor mixing may actually reduce NOx emission.

INTERNATIONAL JOURNAL OF HYDROGEN ENERGY (2022)

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Article Chemistry, Physical

The decreasing effect of ammonia enrichment on the combustion emission of hydrogen, methane, and propane fuels

Mehmet Salih Cellek

Summary: In this study, non-premixed combustion and NOx emission of H-2, NH3, C3H8, and CH4 fuels were investigated. The results showed that H-2 fuel had a high flame temperature, NH3 fuel had the shortest flame length, and C3H8 fuel had the longest flame shape. The highest level of NOx emissions was observed from NH3 fuel in the combustion chamber, while the lowest NOx emissions were observed from CH4 fuel. NH3 enrichment and excess air combustion could significantly reduce the NOx emissions from H(2) and other fuels during combustion.

INTERNATIONAL JOURNAL OF HYDROGEN ENERGY (2022)

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Article Chemistry, Physical

Oxidizer effects on ammonia combustion using a generated non-premixed burner

Mustafa Ilbas et al.

Summary: In this study, the combustion of pure ammonia in a model combustor was investigated to explore ammonia-fueled applications. The effects of oxygen enrichment on flame characteristics, temperature profiles, and NO profiles during ammonia combustion were evaluated, and compared with the combustion of air-ammonia mixture. The results showed that the use of an oxidizer with 100% oxygen content provided better flame stability in pure ammonia combustion. The most stable flame for oxy-ammonia combustion was achieved with an excess oxygen coefficient of 1.0 or 1.2, and the lowest NO levels were observed under fuel-rich conditions. The air-ammonia combustion resulted in a significant decrease in temperature and NO emissions, but flame stabilities were unsatisfactory except under fuel-rich conditions. The oxy-enrichment condition is considered a promising method for pure ammonia combustion, provided that NO emissions can be optimized with NO reduction methods.

INTERNATIONAL JOURNAL OF HYDROGEN ENERGY (2022)

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Article Thermodynamics

Chemical effect of water addition on the ammonia combustion reaction

Qi Zhang et al.

Summary: This study investigates the chemical reactions involved in ammonia oxidation and NOx formation through reaction molecular dynamics simulations. The effects of different environment conditions and water addition on ammonia oxidation behavior and product distribution are analyzed. The results show that water addition can effectively control NOx emissions in ammonia combustion.

THERMAL SCIENCE AND ENGINEERING PROGRESS (2022)

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Article Engineering, Environmental

A technological roadmap to the ammonia energy economy: Current state and missing technologies

Natalia Morlane et al.

Summary: Ammonia is recognized as a key energy carrier with potential applications in low-carbon energy storage, transportation, and power generation. Further research and development are needed to fully utilize its advantages and implement it as a building block in the global low-carbon energy landscape.

CHEMICAL ENGINEERING JOURNAL (2021)

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Article Thermodynamics

An experimental and modeling study of ammonia with enriched oxygen content and ammonia/hydrogen laminar flame speed at elevated pressure and temperature

Krishna Prasad Shrestha et al.

Summary: This study experimentally investigated the laminar flame speeds of ammonia and ammonia-hydrogen blends under different temperature, pressure, and oxygen content conditions, and developed a new kinetic model for predicting the oxidation mechanisms, considering the formation and reduction of nitrogen oxides. The results showed that the laminar flame speed increases with increasing initial temperature, fuel hydrogen content, or oxidizer oxygen content, but decreases with increasing initial pressure. The proposed kinetic model predicts the same trends as experiments and highlights the importance of N2H2 formation under rich conditions.

PROCEEDINGS OF THE COMBUSTION INSTITUTE (2021)

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Article Thermodynamics

The effect of oxygen content on the turbulent flame speed of ammonia/oxygen/nitrogen expanding flames under elevated pressures

Shixing Wang et al.

Summary: Ammonia is a promising carbon-free fuel and hydrogen carrier for renewable energy, with turbulent flame speed found to increase with oxygen content but turbulent-to-laminar flame speed ratio decreasing. The study presents correlations of turbulent flame speed based on Karlovitz number and Damkohler number, showing that ammonia/oxygen/nitrogen mixtures can achieve similar turbulent flame speed as methane/air.

COMBUSTION AND FLAME (2021)

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Review Energy & Fuels

Review on Ammonia as a Potential Fuel: From Synthesis to Economics

A. Valera-Medina et al.

Summary: Ammonia as a fuel vector has been gaining interest and efforts are being made to find new methods to reduce carbon emissions. The current need to decarbonize the economy makes ammonia a viable fuel option, with economic implications being significant.

ENERGY & FUELS (2021)

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Article Chemistry, Physical

Numerical simulation of ammonia/methane/air combustion using reduced chemical kinetics models

Hrvoje Mikulcic et al.

Summary: Ammonia combustion is a potential alternative fuel for hydrogen storage and engine use, with chemical mechanisms being crucial for minimizing harmful emissions. Further research is needed to study combustion kinetics, with the aim of applying insights to industrial burning systems. The study highlights the importance of accurate combustion chemistry modeling for improving emissions control in industrial applications.

INTERNATIONAL JOURNAL OF HYDROGEN ENERGY (2021)

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Article Energy & Fuels

An experimental study of laminar ammonia/methane/air premixed flames using expanding spherical flames

Tao Shu et al.

Summary: Experimental investigation of flame properties in ammonia/methane/air mixtures shows significant influence of gas composition and pressure on flame speeds and flammability limits. Linear correlation between flame speed and methane volume fraction is observed, with accurate prediction using Okafor et al. mechanism.

FUEL (2021)

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Article Energy & Fuels

Chemical Kinetic Modeling of the Autoignition Properties of Ammonia at Low-Intermediate Temperature and High Pressure using a Newly Proposed Reaction Mechanism

Anand Shankar Singh et al.

Summary: The study proposes a new ammonia oxidation reaction model for low to intermediate temperature conditions and high-pressure settings. Through comprehensive chemical kinetic modeling and CFD simulations, the model successfully predicts autoignition properties and weak flame formation of ammonia/air mixtures. Model validation shows excellent agreement between computational and experimental results.

ENERGY & FUELS (2021)

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Article Thermodynamics