SCI和EI收录∣中国化工学会会刊

Chinese Journal of Chemical Engineering ›› 2012, Vol. 20 ›› Issue (4): 701-709.

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Effects of CO2 Dilution on Methane Ignition in Moderate or Intense Low-oxygen Dilution(MILD) Combustion: A Numerical Study

曹甄俊1,2, 朱彤1   

  1. 1. College of Mechanical Engineering, Tongji University, Shanghai 200092, China;
    2. Shanghai DFYH Tech Services Co., Ltd., Shanghai 201114, China
  • 收稿日期:2011-03-02 修回日期:2012-02-18 出版日期:2012-08-28 发布日期:2012-09-15
  • 通讯作者: ZHU Tong, E-mail:zhu_tong@tongji.edu.cn
  • 基金资助:
    Supported by the National Natural Science Foundation of China (50206014);the Shuguang Scholar Program of Shanghai Education Development Foundation (05SG23)

Effects of CO2 Dilution on Methane Ignition in Moderate or Intense Low-oxygen Dilution(MILD) Combustion: A Numerical Study

CAO Zhenjun1,2, ZHU Tong1   

  1. 1. College of Mechanical Engineering, Tongji University, Shanghai 200092, China;
    2. Shanghai DFYH Tech Services Co., Ltd., Shanghai 201114, China
  • Received:2011-03-02 Revised:2012-02-18 Online:2012-08-28 Published:2012-09-15
  • Supported by:
    Supported by the National Natural Science Foundation of China (50206014);the Shuguang Scholar Program of Shanghai Education Development Foundation (05SG23)

摘要: Homogeneous mixtures of CH4/air under moderate or intense low-oxygen dilution(MILD) combustion conditions were numerically studied to clarify the fundamental effects of exhaust gas recirculation(EGR),especially CO2 in EGR gases,on ignition characteristics.Specifically,effects of CO2 addition on autoignition delay time were emphasized at temperature between 1200 K and 1600 K for a wide range of the lean-to-rich equivalence ratio(0.2~2).The results showed that the ignition delay time increased with equivalence ratio or CO2 dilution ratio.Furthermore,ignition delay time was seen to be exponentially related with the reciprocal of initial temperature.Special concern was given to the chemical effects of CO2 on the ignition delay time.The enhancement of ignition delay time with CO2 addition can be mainly ascribed to the decrease of H,O and OH radicals.The predictions of temperature profiles and mole fractions of CO and CO2 were strongly related to the chemical effects of CO2.A single ignition time correlation was obtained in form of Arrhenius-type for the entire range of conditions as a function of temperature,CH4 mole fraction and O2 mole fraction.This correlation could successfully capture the complex behaviors of ignition of CH4/air/CO2 mixture.The results can be applied to MILD combustion as "reference time",for example,to predict ignition delay time in turbulent reacting flow.

关键词: moderate or intense low-oxygen dilution combustion, ignition delay time, autoignition, methane

Abstract: Homogeneous mixtures of CH4/air under moderate or intense low-oxygen dilution(MILD) combustion conditions were numerically studied to clarify the fundamental effects of exhaust gas recirculation(EGR),especially CO2 in EGR gases,on ignition characteristics.Specifically,effects of CO2 addition on autoignition delay time were emphasized at temperature between 1200 K and 1600 K for a wide range of the lean-to-rich equivalence ratio(0.2~2).The results showed that the ignition delay time increased with equivalence ratio or CO2 dilution ratio.Furthermore,ignition delay time was seen to be exponentially related with the reciprocal of initial temperature.Special concern was given to the chemical effects of CO2 on the ignition delay time.The enhancement of ignition delay time with CO2 addition can be mainly ascribed to the decrease of H,O and OH radicals.The predictions of temperature profiles and mole fractions of CO and CO2 were strongly related to the chemical effects of CO2.A single ignition time correlation was obtained in form of Arrhenius-type for the entire range of conditions as a function of temperature,CH4 mole fraction and O2 mole fraction.This correlation could successfully capture the complex behaviors of ignition of CH4/air/CO2 mixture.The results can be applied to MILD combustion as "reference time",for example,to predict ignition delay time in turbulent reacting flow.

Key words: moderate or intense low-oxygen dilution combustion, ignition delay time, autoignition, methane