This study reports experimental results and correlations for axisymmetric gaseous fuel jets restricted by parallel sidewalls at various separation distances. Although many investigations have been conducted to elucidate the flame height evolution of diffusion flames in an unrestricted environment; the restriction effect of sidewalls on diffusion flames, which occasionally occurs in accidental leakages of city natural gas pipelines, has received little attention. The underlying interaction dynamics of axisymmetric gaseous fuel jets with two parallel sidewalls at various separation distances has not been fully elucidated. In this work, a series of experiments on this issue were carried out with 3-, 6- and 10-mm nozzles. The sidewall separation distances were varied from 10 to 50 cm with a corresponding free condition. A series of new results and their interpretation are presented in this work. The results show that the flame height changes little when the sidewall separation distance reduces from +∞ to a critical value (S_cri). Further reductions on the sidewall separation distance from S_cri disturbed the evolution process of uprising vortexes and hindered air entrainment, leading to significant changes to the jet-flame shape by enlarging the flame height. The maximum flame heights had a linear relation with the critical separation distance of the sidewalls at the critical conditions, being consistent with the scaling analysis of the flow field. The dimensionless critical separation distance was found to be well correlated with the dimensionless heat release rate, ${\dot{Q}}_D^{\ast }$, with a 2/5 power law. A global model, characterizing the variation of the flame height with the dimensionless heat release rate, was proposed, showing good agreement with the experimental results. The results and the expressions obtained in this study contribute to a better understanding of jet fires, allowing a better prediction of flame height, relevant to the design of gas fuel storage systems and transportation systems in the city.

这项研究报告了轴对称气态燃料射流的实验结果及其相关性，这些射流受到不同分离距离下平行侧壁的限制。尽管已经进行了许多研究来阐明在不受限制的环境中扩散火焰的火焰高度演变；侧壁对扩散火焰的限制作用很少引起关注，扩散限制火焰偶尔发生在城市天然气管道意外泄漏中。尚未完全阐明具有不同间隔距离的两个平行侧壁的轴对称气体燃料射流的基本相互作用动力学。在这项工作中，使用3毫米，6毫米和10毫米喷嘴对这个问题进行了一系列实验。侧壁间隔距离在10到50 cm之间变化，并具有相应的自由状态。这项工作提出了一系列新的结果及其解释。结果表明，当侧壁间距从+∞减小到临界值时，火焰高度几乎不变（s _cri）。与S _cri的侧壁间隔距离的进一步减小扰动了涡旋的演变过程并阻碍了空气夹带，从而通过增大火焰高度而导致了喷射火焰形状的显着变化。在临界条件下，最大火焰高度与侧壁的临界分离距离呈线性关系，与流场的定标分析一致。发现无因次临界分离距离与无因次放热率有很好的相关性，${\dot{问}}_d^{\ast }$，具有2/5幂定律。提出了表征火焰高度随无因次放热率变化的整体模型，与实验结果吻合良好。在这项研究中获得的结果和表达式有助于更好地理解喷射火，从而更好地预测火焰高度，这与城市中的气体燃料存储系统和运输系统的设计有关。