中文摘要：

对0．1～4．0MPa范围内CH。富氧燃烧层流同轴射流扩散火焰进行了数值研究，研究对象包含3种工况：工况I为CH4／空气，工况2为CH4／70％N2和30％02，工况3为CH4／70％CO2和30％02．计算模型采用了基于GRI3．0的骨干反应机理，该机理包含26种组分和163个反应，同时模型还考虑了CH4、H20、C02、CO的辐射换热损失．结果表明，富氧燃烧使火焰温度升高、长度变短．工况2中NO排放指数与T况1相比增加了70％，且随压力的提高而增大，绝大部分NO是通过热力型NO途径形成．基元反应H＋C02≠OH＋CO使得工况3近燃烧器喷口处的CO浓度大大增加．提高压力，火焰温度先升高后降低，火焰半径逐渐变小，火焰长度几乎不变．

英文摘要：

Numerical study of three axisymmetric laminar co-flow diffusion flames at pressures between 0.1- 4.0 MPa was conducted. One flame is a methane/air flame （Flame 1）, and the other two are methane/nitrogen-diluted oxygen flame （Flame 2） and methane/carbon dioxide -diluted oxygen flame （Flame 3）, the mass fraction of oxygen in the oxidizer of Flame 2 and Flame 3 are both 30%. Numerical model includes a skeletal mechanism derived from GRI- Mech 3.0 with 163 reaction steps and 26 species. An optically thin radiation sub-model was employed in the simula- tions to consider the thermal radiation absorption by species such as CH4, CO2, CO and H20. As compared to Flame 1, the two oxygen-enhanced combustion flames are shorter and hotter. NO emission index in Flame 2 increases by 70% and increase monotonically with pressure. The majority of NO in Flame 2 is produced via the thermal route. The reaction step： H ＋ CO2 = OH ＋ CO accounts for the high the pressure increases, flame temperature increases firstly mole fraction of CO in Flame 3 near the fuel tube exit. As and then decreases, flame radius decreases monotonically,while flame height remains almost constant.