The chemical mechanism of steam’s effect on the temperature in methane oxy-steam combustion
The chemical mechanism of steam’s effect on the temperature in methane oxy-steam combustion
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DOI：
10.1016/j.ijheatmasstransfer.2014.03.051
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发表时间：
2014-08
影响因子：
5.2
通讯作者：
C. Zou;Yu Song;Li Guoyuan;Cao Shiying;Yizhuo He;C. Zheng
中科院分区：
文献类型：
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作者：
C. Zou;Yu Song;Li Guoyuan;Cao Shiying;Yizhuo He;C. Zheng
数值模拟研究了甲烷氧-蒸汽燃烧过程中蒸汽对温度的化学影响，详细分析了化学反应机理，研究了蒸汽对甲烷氧-蒸汽燃烧过程中火焰温度的影响。当氧化剂中水蒸气的摩尔分数为72.5%时，氧-水蒸气燃烧的温度分布与传统燃烧的温度分布一致。通过比较加入水蒸气时的最高温度和相应的人工材料X的加入量，发现当H2O（或X）的摩尔分数在0.60 ~ 0.66之间时，水蒸气的化学效应达到峰值。与传统燃烧相比，空气中的高水蒸气浓度增强了三体反应，提高了OH的浓度，并且降低了氧-水蒸气燃烧期间H的浓度。因此，当水蒸气的摩尔分数在0.5和0.7之间时，三体反应（H+ O 2+ H 2 O惠HO 2+ H 2 O）（R35）是决定氧-水蒸气燃烧过程中燃烧温度的关键基元反应;该反应还向R287提供足够的HO 2，使R287具有最高的放热速率。当蒸汽摩尔分数超过0.75时，降低的氧摩尔分数提高了CO的产生速率。同时，R38是决定燃烧温度的关键基元反应，因为它提供了大量的自由基OH物种。因此，R99优于R287，具有最高的热释放速率。当水蒸气摩尔分数为0.725时，R35和R38对燃烧温度的影响很大，R99对温度的贡献最大，R287和R43对温度的贡献也很大。
A numerical study with a detailed chemistry mechanism has been conducted to investigate the chemical effects of steam on the temperature in methane oxy-steam combustion; steam is used to moderate the high flame temperature produced by combustion of the fuel using oxygen. The temperature profiles of the oxy-steam combustion are consistent with those of traditional combustion when the mole fraction of steam in the oxidant is 72.5%. The comparisons between the maximum temperatures when steam is added and the corresponding artificial material X addition reveal that when the mole fraction of H 2 O (or X) is between 0.60 and 0.66, the overall chemical effects of the steam peak. High steam concentration in the atmosphere enhances the three-body reaction, raises the concentration of OH, and lowers the concentration of H during oxy-steam combustion, in contrast to traditional combustion. Consequently, when the steam’s mole fraction is between 0.5 and 0.7, the three-body reaction (H+ O 2+ H 2 O⇔ HO 2+ H 2 O)(R35) is the key elementary reaction that determines the combustion temperature during oxy-steam combustion; this reaction also provides sufficient HO 2 to R287, giving R287 the highest heat release rate. When the steam mole fraction exceeds 0.75, the reduced oxygen mole fraction enhances the rate of CO production. Concurrently, R38 is the key elementary reaction for determining the combustion temperature because it supplies a large amount of radical OH species. Therefore, R99 dominates R287 and has the highest heat release rate. When the steam mole fraction is 0.725, R35 and R38 play a very important role affecting the combustion temperature; R99 makes the largest contribution to temperature, while R287 and R43 also make significant contributions to the temperature.