Premixed and non-premixed flames of CH₄/O₂ are widely used in industrial fields, including the non-catalytic partial oxidation (NC-POX) of natural gas to produce hydrogen-rich syngas. As a major spontaneous emission present in flames, OH^∗ chemiluminescence is often applied in combustion diagnostics to indicate flame structure, reaction mechanism and equivalence ratio. In this study, the flame imaging technique was applied in order to investigate the flame structure, lift-off height, peak OH^∗ intensity and core reaction zone for a CH₄/O₂ lifted flame impinging a plate. The results demonstrated that both the increase in the global equivalence ratio (λ) as well as the reduction in the plate-to-nozzle distance (L/De) can contribute the generation of the lifted flame. In regard to the fixed L/De, the lifted flame exhibited a narrower flame front and lower chemical reaction intensity in the case of a small λ. As L/De decreased, the position of the flame core reaction zone shifted to the flame base. Meanwhile, the core reaction zone of the flame and peak OH^∗ intensity was found to increase progressively. In addition, with the increase in λ, the flame lift-off height (H) initially rose gradually, after which it then declined sharply and thereafter increased. As indicated by the flame lift-off characteristic, as λ rose, a circulation zone developed at the flame base, which was located between the flame inner shear layer and the jet of oxidizer. Accordingly, the circulation zone can promote the generation of a lifted flame due to the enhanced mixing of the reactants.

CH ₄ /O _{2 的}预混和非预混火焰广泛应用于工业领域，包括天然气的非催化部分氧化（NC-POX）生产富氢合成气。作为火焰中存在的主要自发辐射，OH ^*化学发光常用于燃烧诊断以指示火焰结构、反应机理和当量比。在本研究中，应用火焰成像技术来研究CH ₄ /O ₂的火焰结构、提升高度、峰值 OH ^*强度和核心反应区升起的火焰撞击盘子。结果表明，整体当量比 (λ) 的增加以及板到喷嘴距离 ( L / De ) 的减少都有助于产生离火。对于固定的L / De，在小 λ 的情况下，离火火焰呈现出更窄的火焰前沿和更低的化学反应强度。随着 L/ De 的减小，火焰核心反应区的位置向火焰底部移动。同时，发现火焰的核心反应区和峰值 OH ^*强度逐渐增加。此外，随着 λ 的增加，火焰抬升高度（H) 最初逐渐上升，之后急剧下降，随后上升。由火焰升起特性表明，随着λ的增加，在火焰底部形成一个循环区，位于火焰内部剪切层和氧化剂射流之间。因此，由于反应物的增强混合，循环区可以促进升焰的产生。