The present study investigated experimentally the effects of relative strong crosswinds on the flame geometry characteristics (flame height and flame horizontal length) from carriage fires in a tunnel, which have not been quantified previously. Overall 144 test conditions were involved for various heat release rates, crosswind speeds and opening sizes. It was found that, with increase in crosswind speed till relative strong conditions, the flame height first decreased then remained nearly unchanged, while the flame horizontal length first increased then decreased. Finally, the flame is blown-off at strong crosswind conditions. A physical model is proposed to interpret and characterize the evolution behavior of these flame geometry characteristics with crosswind till relative strong condition. Two non-dimensional parameters, the wind Froude number and the dimensionless excess heat release rate, were found based on the analysis of the controlling mechanisms including the flame tilt and air combustion with excess fuel outside the carriage. The experimental results were shown to be well represented by the proposed parameters. This study provides quantitative data and basic understanding of the flame geometry characteristics under relative strong crosswinds from carriage fires in a tunnel.

本研究通过实验研究了相对强的侧风对隧道内马车火灾的火焰几何特征（火焰高度和火焰水平长度）的影响，而此前尚未进行量化。总共144个测试条件涉及各种放热率，侧风速度和开孔尺寸。发现，随着侧风速度的增加直到相对强的条件，火焰高度先降低然后保持几乎不变，而火焰水平长度先增加然后降低。最后，火焰在强侧风条件下被吹散。提出了一个物理模型来解释和表征这些火焰几何特征在侧风直至相对强的条件下的演化行为。两个无量纲参数，通过对控制机理的分析，包括火焰倾斜和车架外部过量燃料的空气燃烧，发现了弗洛德数和无因次的过量放热率。实验结果表明可以很好地代表所提出的参数。这项研究提供了定量数据和对隧道交通中相对强侧风的火焰几何特征的基本理解。