Systematic review on ammonia as a sustainable fuel for combustion

Ammonia, with its high hydrogen content, serves as an efficient energy carrier and a potential replacement for traditional fossil fuels in achieving the United Nations ' carbon neutrality goal. It also offers significant advantages over hydrogen in production, storage, and transportation. Extensive research has been conducted on the use of ammonia for transportation and power generation, collectively referred to as ammonia for combustion (AFC). However, there remains a lack of systematic review in this area, which this study aims to address. Using bibliometric techniques, data from research publications spanning 2000 to 2024 were gathered from the Web of Science database, revealing that publication numbers remained low until 2015 but increased significantly from 2016 onward. This research systematically analyzes numerical and experimental studies on combustion characteristics and technologies across the last forty years. The primary challenges identified with AFC include prolonged ignition delay, low laminar burning velocity, and high NOx emissions. To mitigate these challenges, various technologies such as fuel blending and auxiliary combustion technologies have been proposed. The review also highlighted a lack of research concerning technology readiness levels for AFC. To address this gap, a comprehensive examination of various applications such as internal combustion engines, marine engines, aircraft engines, and gas turbines for power generation was undertaken. This evaluation encompassed objectives, research gaps, methods for enhancing performance, and assessments of technology readiness levels. The findings of this investigation make substantial contributions to the field, offering valuable insights into the challenges and prospects of ammonia as a sustainable fuel for combustion.