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首页> 外文期刊>Journal of the Chinese Society of Mechanical Engineers, Series C: Transactions of the Chinese Society of Mechanical Engineers >A numerical analysis of flame spread over a thin fuel inclined from vertically downward to horizontal
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A numerical analysis of flame spread over a thin fuel inclined from vertically downward to horizontal

机译：火焰在稀薄燃料上扩散的数值分析，燃料从垂直向下倾斜到水平

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摘要

The behavior of flame spreading downward over a thin inclined sheet of solid fuel is analyzed numerically in this paper. Since the flame spread has both constant and unsteady flame-spread rate characteristics at different inclinations, a combustion model was developed to study the inclination effect. An unsteady solid phase is coupled with a quasi-steady gas phase via the linkage of mass and energy balance to solve the problem with progression over time. Since the computations are very time-consuming, the model was applied to the downward flame spread problem at only four inclination angles, 90°, 60°, 30° and 0°. The parametric study showed that a constant flame-spread rate flame propagation is still retained at inclination angles of 90° and 60°. But solid fuel inclined at 30° and 0° exhibit unsteady flame-spread rates with nearly periodic accelerations and decelerations. Investigating unstable mechanisms in horizontal flame spread, we find the primary one is that the fuel supply rate by mass diffusion can not match the fuel consumption rate in the flame reaction. The heat flux from the gas phase in the preheat zone is found to be a dominant heat transfer mechanism to accelerate and decelerate flame spread. A comparison made with a constant-rate horizontal flame spread model shows that the unsteady model presented here is better suited to study the problem of unstable flame spread, both on unsteady characteristics and flame-spread rate values.
机译：数值分析了火焰在薄薄的固体燃料薄板上向下扩散的行为。由于火焰传播在不同的倾斜度下都具有恒定和不稳定的火焰传播速率特性，因此开发了燃烧模型来研究倾斜效果。不稳定的固相与准稳定的气相通过质量和能量平衡的联系而耦合，以解决随时间推移而发生的问题。由于计算非常耗时，因此该模型仅以四个倾角90°，60°，30°和0°应用于向下的火焰扩散问题。参数研究表明，在90°和60°倾斜角下，火焰传播速率仍保持恒定。但是，以30°和0°倾斜的固体燃料表现出不稳定的火焰扩散速率，几乎具有周期性的加速和减速。通过对水平火焰传播的不稳定机理进行研究，我们发现主要的原因是通过质量扩散产生的燃料供给速率不能与火焰反应中的燃料消耗速率相匹配。发现来自预热区中气相的热通量是主要的传热机制，可加速和减速火焰扩散。与恒定速率水平火焰传播模型进行的比较表明，此处介绍的非稳态模型更适合于研究不稳定火焰传播的问题，包括非稳态特征和火焰传播速率值。

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