Effects of OH concentration and temperature on NO emission characteristics of turbulent non-premixed CH4/NH3/air flames in a two-stage gas turbine like combustor at high pressure

Kapuruge Don Kunkuma Amila Somarathne, Ekenechukwu C. Okafor, Daiki Sugawara, Akihiro Hayakawa, Hideaki Kobayashi

研究成果: Conference article査読

2 被引用数 (Scopus)

抄録

The effects of OH concentration and temperature on the NO emission characteristics of turbulent, non-premixed CH4/NH3/air swirl flames in two-stage combustors at high pressure were studied. Emission data were obtained using large-eddy simulations with a finite-rate chemistry method from model flames based on the energy fraction of NH3 (ENH3) in CH4/NH3 mixtures. NO emissions at the combustor exit were significantly higher than those generated by CH4/air and NH3/air flames under both lean and stoichiometric primary zone conditions. These emissions were reduced to ~300 ppm by using far-rich equivalence ratios (Φ) of 1.3-1.4 in the primary zone. This effect was possibly due to the lower OH concentrations under far-rich conditions. An analysis of local flame characteristics using a newly developed mixture fraction equation for CH4/NH3/air flames indicated that the local temperature and NO and OH concentration distributions with local Φ were qualitatively similar to those in NH3/air flames. The maximum local NO and OH concentrations appeared at local Φ of 0.9, although the maximum temperature was observed at local Φ of 1.0. Both the temperature and OH concentration gradually decreased with the partial replacement of CH4 with NH3. Consequently, NO emissions from CH4/NH3 flames were maximized at ENH3 in the range of 20-30%, after which the emissions decreased. Above 2100 K, the NO emissions from CH4/NH3 flames increased exponentially with temperature, which was not observed in NH3/air flames because of the lower flame temperatures in the latter. However, the maximum NO concentration in CH4/NH3 flames occurred at a temperature slightly below the maximum temperature, just as in NH3/air flames. The apparent exponential increase in NO emissions from CH4/NH3 flames was attributed to a similar trend in the OH concentration at high temperatures.

本文言語English
ページ(範囲)5163-5170
ページ数8
ジャーナルProceedings of the Combustion Institute
38
4
DOI
出版ステータスPublished - 2021
イベント38th International Symposium on Combustion, 2021 - Adelaide, Australia
継続期間: 2021 1 242021 1 29

ASJC Scopus subject areas

  • 化学工学(全般)
  • 機械工学
  • 物理化学および理論化学

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