Flame attachment and kinetics studies of laminar coflow CO/H-2 diffusion flames burning in O-2/H2O
Flame attachment and kinetics studies of laminar coflow CO/H-2 diffusion flames burning in O-2/H2O
复制标题
O-2/H2O 中层流 CO/H-2 扩散火焰燃烧的火焰附着和动力学研究
DOI：
10.1016/j.combustflame.2018.06.003
复制
发表时间：
2018
影响因子：
4.4
通讯作者：
Shaozeng Sun
中科院分区：
文献类型：
--
作者：
Huanhuan Xu;Fengshan Liu;Shaozeng Sun
本文采用实验和数值模拟相结合的方法，研究了层流CO/H_2扩散火焰在同向流动O_2/H_2O中燃烧、入口温度为400 K时燃料和氧化剂的附着和氧化过程。考察了CO/H_2摩尔比从95%CO-5%H_2到5%CO-95%H_2以及纯H_2对燃料组成的影响。该氧化剂的固定组成为75%H2O-25%O2。利用OH~*化学发光图像所测得的火焰高度来验证本文所采用的火焰模型。通过对预热效应、反应机理和热输运特性的二维火焰程序的数值模拟，得到并分析了火焰附着和火焰结构的细节。尽管CO和H_2都在燃烧器边缘扩散，并向上游进入氧化剂气流，但富H_2合成气火焰的附着点比富CO火焰在燃烧器出口下方的上游更远。这归因于H2通过反应OH + H2= H + H2O的高反应性和H2的高扩散系数。在详细的动力学分析的基础上，揭示了合成气在O2/H2O氧化剂中燃烧的反应路径，不仅在燃料管内和燃料出口上方，而且在火焰片附近和火焰附着区。由于OH + H2= H + H2O的反向反应，在火焰核心观察到大量的H2O消耗，如果燃料流动中有丰富的H2，则该反应在火焰外部的径向方向上也向前移动，将未燃烧的H2氧化为H2O。
In this study, experimental and numerical investigations were conducted to study the attachment and oxidation process of laminar CO/H2diffusion flames burning in coflow O2/H2O at 1 atm with an inlet temperature of 400 K for both the fuel and oxidizer streams. The effects of fuel composition were investigated by considering a wide range of CO/H2mole ratio from 95%CO–5%H2to 5%CO–95%H2and also pure H2. The oxidizer has a fixed composition of 75%H2O–25%O2. The measured flame heights determined by OH*-chemiluminescence images were used to validate the flame model adopted in this work. Through numerical simulations using a two-dimensional flame code with the preheating effect, detailed reaction mechanism, and detailed thermal and transport properties, the details of flame attachment and flame structure were obtained and analysed. Although both CO and H2diffuse over the burner rim and move upstream into the oxidizer stream, the attachment point of a H2-rich syngas flame is further upstream below the burner exit than that of a CO-rich flame. This is attributed to the high reactivity of H2through reaction OH + H2= H + H2O and the high diffusivity of H2. Reaction pathways for syngas burning in the oxidizer of O2/H2O based on a detailed kinetics analysis were revealed, not only inside the fuel tube and above the fuel exit, but also near the flame sheet and in the flame attachment zone. Significant consumption of H2O was observed in the flame core due to the reverse reaction of OH + H2= H + H2O which shifts to proceed forward outside the flame in the radial direction also at higher streamwise locations if H2in the fuel flow is rich, oxidizing unburned H2to H2O.