Stretch extinction characteristics of CH4/CO2 versus O-2/H2O/CO2 and O-2/H2O counterflow non-premixed flames at different oxidizer temperatures
Stretch extinction characteristics of CH4/CO2 versus O-2/H2O/CO2 and O-2/H2O counterflow non-premixed flames at different oxidizer temperatures
复制标题
不同氧化剂温度下 CH4/CO2 与 O-2/H2O/CO2 和 O-2/H2O 逆流非预混火焰的拉伸熄灭特性
DOI：
10.1016/j.fuel.2016.09.017
复制
发表时间：
2016
期刊：
影响因子：
7.4
通讯作者：
Zhao Daiqing
中科院分区：
文献类型：
--
作者：
Li Xing;Yang Haolin;Jiang Liqiao;Wang Xiaohan;Zhao Daiqing
燃烧环境中CO2和H2O的浓度对于使用含有大量CO2和/或H2O的热氧化剂的富氧火焰的燃烧特性非常重要。为了了解富氧火焰的火焰温度和拉伸熄灭极限随H2O和CO2浓度的变化，对氧摩尔分数为0.35的CH4/CO2与O2/H2O/CO2和O2/H2O逆流非预混火焰进行了数值研究，并与氧化器处的CH4/CO2与O2/CO2(XO2=0.35)火焰进行了比较。温度分别为 500、700 和 1000 K。研究中使用两种具有不同 H2O 和 CO2 浓度的 O2/H2O/CO2 混合物作为氧化剂。结果表明，当氧化剂中的CO2被H2O取代时，火焰温度和熄灭应变率均升高。基于理论解和计算结果的分析表明，火焰的OH自由基总量可以作为拉伸消光极限比较的标准。计算结果表明，当氧化剂中添加 H2O 时，O + H2O = 2OH 反应产生 OH 自由基的速率与 H + O2= O + OH 的速率相当。随着氧化剂中H2O摩尔分数的增加，O + H2O = 2OH产生的OH自由基数量增加，导致消光应变率显着增加。
The concentrations of CO2and H2O in the combustion environment are important for the combustion characteristics of oxygen-enriched flames using hot oxidizers with large amount of CO2and/or H2O. To understand the variations of flame temperature and stretch extinction limit of oxygen-enriched flames with H2O and CO2concentrations, the CH4/CO2versus O2/H2O/CO2and O2/H2O counterflow non-premixed flames with the oxygen mole fraction of 0.35 were investigated numerically and compared with those of the CH4/CO2versus O2/CO2(XO2= 0.35) flames at the oxidizer temperatures of 500, 700 and 1000 K. Two O2/H2O/CO2mixtures with different H2O and CO2concentrations were used as the oxidizers in the study. The results show that the flame temperature and the extinction strain rate are increased when the CO2in the oxidizer has been replaced by H2O. The analysis based on the theoretical solution and computational result suggests that the total amount of OH radicals of the flame can be used as a criterion for the comparison of stretch extinction limit. The computational results show that the production rate of OH radicals via the reaction O + H2O = 2OH is comparable to that of H + O2= O + OH when H2O is added in the oxidizer. And the amount of OH radicals generated by O + H2O = 2OH increases with increasing H2O molar fraction of the oxidizer, resulting in a significant increase of the extinction strain rate.