Study on the discharge and emission characteristics of rotating gliding arc plasma using air, ammonia, and ammonia/air mixtures

Due to the application limitations of ammonia as a clean energy source, plasma-assisted combustion technology has become an effective method to improve ammonia combustion performance. This study investigates the discharge characteristics of rotating gliding arc (RGA) plasma in air, ammonia, and ammonia/air mixed gases, as well as their effects on combustion and emissions. Studies have shown that increasing the RGA plasma power enhances the stability of the gas discharge voltage and current waveforms, promotes the combustion reaction of the mixed gas, and shortens the flame when high ammonia content is present. In the ammonia discharge spectrum, NH, N₂, Hα, and Hβ are primarily observed, while in the air discharge, NO, N₂, OH, and O are mainly observed. The discharge spectrum of mixed gas containing 10% ammonia is mainly composed of substances common to both discharges, with the intensity of OH emissions significantly increasing as power increases. Under varying ammonia concentrations and discharge power conditions, the introduction of RGA plasma can extend the combustion range of ammonia from 20-25% to 15%. When the ammonia content is low (less than 15%), the NO generated by air discharge is reduced due to the reduction reaction of ammonia. When the ammonia content exceeds 15%, the NO concentration increases with rising power. If the discharge power is less than 10% of the combustion power (power ratio), the NO produced is either less than or comparable to the NO generated by ammonia combustion without plasma. However, when the power ratio exceeds 10%, the combustion reaction is enhanced, leading to a sharp increase in NO emissions. The combustion reaction temperature of the mixture steadily increases as the power increases. These findings offer valuable insights into optimizing the plasma-assisted ammonia combustion process, enhancing combustion efficiency and minimizing pollutant emissions, thereby improving environmental sustainability.