Journal of the Korean Institute of Gas (한국가스학회지)

The Korean Institute of GAS (한국가스학회)
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Numerical Study on Ignition Delay Time of CH4 as CO/H2 Addition in MILD Combustion

MILD 연소 환경에서 CO/H2 첨가에 따른 CH4의 점화 지연 시간의 해석적 연구

  • Kim, Donghee (Dept. of Mechanical Engineering, Pohang University of Science and Technology) ;
  • Huh, Kang Y. (Dept. of Mechanical Engineering, Pohang University of Science and Technology) ;
  • Lee, Youngjae (Clean Energy R&D Department, Korea Institute of Industrial Technology)
  • 김동희 (포항공과대학교 기계공학과) ;
  • 허강열 (포항공과대학교 기계공학과) ;
  • 이영재 (한국생산기술연구원 청정에너지시스템)
  • Received : 2021.01.15
  • Accepted : 2021.03.23
  • Published : 2021.04.30
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Abstract

MILD(Moderate or Intense Low-oxygen Dilution) combustion has attracted attention as the clean thermal energy technology due to the lower emissions of unburnt carbon and NOx. MILD combustion aims to enlarge the combustion reaction zone using the spontaneous ignition phenomenon of the reactants. In this study, the ignition delay time of CH4 according to the initial temperature of reactants and the addition of CO, H2 was investigated using a numerical approach. Ignition delay time became shorter as the increases of initial temperature and H2 addition. But, CO addition to the fuel increase the ignition delay time. In case of H2 addition to the fuel, the ignition delay time decreased because the higher fraction of HO2 promotes the decomposition of methyl radical(CH3) and produce OH radical. However, in case of CO addition to the fuel, ignition delay time inceased because a high proportion of HCO consumes H radical. There was no significant effect of HCO on the reduction of ignition delay time. Also, the increase rates of NO emissions by the addition of CO and H2 were approximately 7% and 1%, respectively. A high proportion of NCO affects the increase in NO production rate.

MILD(Moderate or Intense Low-oxygen Dilution) 연소는 열에너지 분야에서 배출되는 미연 탄소와 질소 산화물을 저감하기 위한 기술로, 친환경 열 에너지 생산 기술로 평가받고 있다. MILD 연소 기술은 반응물의 예열을 통한 자발화 현상을 이용하여, 연소 반응 영역을 확장시키는 것이 핵심이다. 본 연구는 CH4와 공기를 활용하여 반응물의 초기 온도 변화와 CO, H2의 혼합율에 따른 CH4의 점화 지연 시간을 수치 해석적 접근을 통해 분석하였다. 점화 지연 시간은 초기 온도와 H2 혼합율이 높을수록 감소하였고, CO 혼합율이 높을수록 증가하였다. 이는 H2 첨가 시 초기에 높은 분율의 HO2가 메틸 라디칼(CH3)의 분해 반응을 촉진시켜 OH를 생성하였기 때문이며, CO 첨가 시 HCO 생성에 따른 H 라디칼 소모가 증가했기 때문이다. 하지만 HCO의 생성은 점화 지연 시간에 큰 영향을 주지 않았다. 또한 연료 내 CO와 H2를 30% 혼합한 조건에서는, NO 배출량이 각각 7%, 1% 증가하는 경향을 보였다. 이는 CO를 혼합한 조건에서 초기에 높은 NCO가 NO 생성반응률 증가에 영향을 미쳤기 때문이다.

Keywords

Acknowledgement

이 논문은 2021년도 정부(산업통상자원부)의 재원으로 한국에너지기술평가원의 지원을 받아 수행된 연구임(20181110200190, 미세먼지 배출저감을 위한 석탄화력 발전소 초 저NOx 연소기술 개발).

References

  1. Kim, Y. P., "Research and Policy Directions against Ambient Fine Particles", J. Korean Soc Atmos Environ, 33(3), 191-204, (2017) https://doi.org/10.5572/KOSAE.2017.33.3.191
  2. Medwell, P. R., Kalt, P. A. M., and Dally, B. B., "Imaging of Diluted Turbulent Ethylene Flames Stabilized on a Jet in Hot Coflow (JHC) Burner", Combust Flame, 152(1-2), 100-113, (2008) https://doi.org/10.1016/j.combustflame.2007.09.003
  3. Wunning, J. A., and Wunning, J. G., "Flameless Oxidation to Reduce Thermal No-formation", Prog Energy Combust Sci, 23(1), 81-94, (1997) https://doi.org/10.1016/S0360-1285(97)00006-3
  4. Cavaliere, A., and de Joannon, M., "Mild Combustion", Prog Energy Combust Sci, 30(4), 329-366, (2004) https://doi.org/10.1016/j.pecs.2004.02.003
  5. Yizhuo, H., Chun, Z., Yu, S., Yang, L., and Chuguang, Z., "Numerical Study of Characteristics on NO Formation in Methane MILD Combustion with Simultaneously Hot and Diluted Oxidant and Fuel (HDO/HDF)", Energy, 112, 1024-1035, (2016) https://doi.org/10.1016/j.energy.2016.07.020
  6. Bahlouli, K., Atikol, U., Saray, R. K., and Mohammadi, V., "A Reduced Mechanism for Predicting the Ignition Timing of a Fuel Blend of Natural-gas and n-hepthane in HCCI Engine", Energy Convers Manage, 79, 85-96, (2014) https://doi.org/10.1016/j.enconman.2013.12.005
  7. Desantes, J. M., Garcia-Oliver, J. M., Vera-Tudela, W., Lopez-Pintor, D., Schneider, B., and Boulouchos, K., "Study of Ignition Delay Time and Generalization of Auto-ignition for PRFs in a RCEM by Means of Natural Chemiluminescence", Energy Convers Manage, 111, 217-228, (2016) https://doi.org/10.1016/j.enconman.2015.12.052
  8. Sabia, P., de Joannon, M., Picarelli, A., Chinnici, A., and Ragucci, R., "Modeling Negative Temperature Coefficient Region in Methane Oxidation", Fuel, 91(1), 238-245, (2012) https://doi.org/10.1016/j.fuel.2011.07.026
  9. Sabia, P., de Joannon, M., Picarelli, A., and Ragucci, R., "Methane Auto-ignition Delay Times and Oxidation Regimes in MILD Combustion at Atmospheric Pressure", Combust Flame, 160, 47-55, (2013) https://doi.org/10.1016/j.combustflame.2012.09.015
  10. Holton, M. M., Gokulakrishnan, P., Klassen, M. S., Roby, R. J., and Jackson, G. S., "Autoignition Delay Time Measurements of Methane, Ethane, and Propane Pure Fuels and Methane-Based Fuel Blends", J. Eng. Gas Turbines Power, 132(9), 091502, (2010) https://doi.org/10.1115/1.4000590
  11. Smith, G. P., Golden, D. M., Frenklach, M., Moriarty, N. W., Eiteneer, B., Goldenberg, M., Bowman, C. T., Hanson, R. K., Song, S., Gardiner Jr, W. C., Lissianski, V. V., and Qin, Z., "What's New in GRI-Mech 3.0", Retrieved from http://combustion.berkeley.edu/gri-mech/version30/text30.html
  12. Kim, D., Huh, K. Y., and Lee, Y., "Experimental Study of Flameless Combustion of Methane in Oxygen-Enriched Condition", J. Korean Soc Combust, 25(3), 1-10, (2020) https://doi.org/10.15231/jksc.2020.25.3.001
  13. Lavoie, G. A., Heywood, J. B., Keck, J. C., "Experimental and Theoretical Study of Nitric Oxide Formation in Internal Combustion Engines", Combust Sci Technol, 1(4), 313-326, (1970) https://doi.org/10.1080/00102206908952211