The critical condition of ghosting flame state in the enclosed tunnel

The purpose of this study is to clarify the unity of the critical conditions of ghosting flame in enclosed tunnel, and to establish a general criterion suitable for the determination of ghosting flame state in vitiated tunnel fire. The ghosting flame in vitiated tunnel fire going through three processes: detachment, oscillation, and ghosting, which are different from traditional compartment ghosting flame. The critical oxygen concentration and critical oxygen consumption rate of ghosting flame are linearly related to the fire source height and heat release rate, respectively. Meanwhile, the criteria to determine the critical conditions proposed in this paper agrees well with the data in previous work. Furthermore, a model that characterizes the critical conditions was established considering the formation process of ghosting flame in vitiated tunnel fire. This work promotes the fundamental understanding of ghosting flame phenomenon in confined tunnel fire and benefits the development of fire protection engineering practice in the future.