A comprehensive review of ammonia combustion: Fundamental characteristics, chemical kinetics, and applications in energy systems

Ammonia has garnered increasing attention as a potential carbon-free fuel due to its zero-carbon emissions, high volumetric energy density, and well-established production, storage, and transportation technologies. Despite these advantages, its poor ignition characteristics, low flame speed, and high NOx emissions pose challenges for widespread application in power generation systems. This review provides a comprehensive overview of both the fundamental combustion characteristics and chemical kinetic mechanisms of ammonia and ammonia blends, as well as their practical utilizations in gas turbines and internal combustion engines. First, the experimental studies on ignition delay times, laminar flame speeds, and oxidation products of ammonia and its blends are reviewed, with an emphasis on the operational conditions that have not been thoroughly addressed in existing studies. The applicability and differences of various chemical kinetic mechanisms in predicting ignition delay, flame speed, and species concentration are discussed in detail, along with the underlying causes of these discrepancies. Second, the review highlights recent advancements in the utilization of ammonia in gas turbines and internal combustion engines. Key aspects such as flame structure, pollutant emission characteristics, stable combustion ranges, and the challenges of achieving efficient and clean ammonia combustion are examined. Strategies for overcoming these challenges and enhancing the performance and emission characteristics of ammonia-fueled systems are also discussed. This work provides a holistic assessment of ammonia combustion, offering insights into both its fundamental behavior and its potential as a sustainable fuel for future power generation systems.