This paper is a re-examination to quantify the flame tilt angle of fires induced by stack effect from a heat and mass transfer perspective. In previous studies, the critical transition and length of the deflection flame were formulated. In the current study, with different kinds of fuels, the flame tilt angles under different strength of stack effect are compared. Results show that under stack effect, the flame tilt angles are quite close at the quasi-steady state within a narrow range regardless of the heat release rate of fire and the position of the open window in a stairwell, which indicates that the inertial force of air flow induced by the stack effect equilibrates dynamically with the thermal buoyancy induced by fire plume. However, the velocity of air flow drawn into the fire compartment is directly related to the strength of stack effect, which is mainly influenced by the heat release rate of fire. A new correlation for the flame tilt angle under the influence of stack effect is developed by taking the dynamic equilibrium into account. The tangent value of the flame tilt angle is linearly proportional to the 4/15 power of the heat release rate of fire. Additionally, a correlation to predict the heat release rate with the titled flame length and flame tilt angle is formulated.

中文翻译：

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烟囱效应下隔室火灾的放热率、火焰倾角和火焰长度的相互作用

本文是对从传热传质角度量化烟囱效应引起的火灾的火焰倾斜角的重新审视。在以前的研究中，偏转火焰的临界转变和长度被公式化了。在目前的研究中，比较了不同燃料在不同烟囱效应强度下的火焰倾斜角。结果表明，在烟囱效应下，无论火焰的热释放率和楼梯间开窗的位置如何，在准稳态下的火焰倾斜角都非常接近，在狭窄的范围内，这表明惯性力为烟囱效应引起的气流与火羽引起的热浮力动态平衡。然而，吸入防火隔间的气流速度与烟囱效应的强度直接相关，这主要受火灾的热释放速率的影响。通过考虑动态平衡，建立了烟囱效应影响下火焰倾斜角的新关系式。火焰倾斜角的正切值与火焰放热率的 4/15 次方成线性正比。此外，还制定了预测热释放率与标题火焰长度和火焰倾斜角的相关性。