超细水雾影响小型火焰在固体可燃物上蔓延的数值模型

开发了CFD模型，用来预测细水雾中火焰沿固体燃料蔓延的特性。采用气体和固体燃料作为对比试验，利用不稳定两维保守公式描述自持性火焰蔓延情况。因为的分析重点主要放在火焰前锋火焰的熄灭机理（火焰前锋完全暴露在细水雾中），所以考虑了有限率（finite—rate）化学反应。火焰基本传播数据也可虑了用于细水雾和蒸气质量的公式，这包括水蒸发造成的能量消耗。还对在细水雾喷洒下聚合材料做成的厚燃料床上火焰的水平传播进行了试验。结果显示，火焰热释放区内自持性能量守恒对外部能量消耗非常敏感。在本试验中，主要是水滴蒸发造成的能量消耗。因此，在火焰前锋，火焰在细水雾的喷洒下挣扎着，要么按几乎相同的速度（没有水喷雾情况下）继续传播，要么被完全熄灭。本文还研究了水滴直径大于30μm细水雾的灭火特性。本文获得了在不同条件下火焰蔓延情况下，灭火需要的细水雾质量分率的关键浓度。

Numerical modeling of the effect of fine water mist on the small scale flame spreading over solid combustibles

A CFD model has been developed to predict the behavior of the flame spread over solid fuels in water mist environment. A coupled analysis involving gas phase and solid fuel is considered using unsteady two-dimensional conservation equations describing the self-sustained flame propagation. Due to the analysis is focused on the mechanism of flame suppression at the flame leading edge, which is explicitly exposed to the mist, finite-rate chemical reaction is taken into account. The equations for water mist and vapor mass fractions are added to the basic flame spread statement, which includes corresponding term describing energy consumption due to water evaporation. Horizontal flame spread over thick fuel beds of polymeric material (PMMA) under water mist suppression has been investigated. The results have shown that self-sustained energy balance in the heat release zone in the flame is highly sensitive to the external energy loss, which in this case is due to water droplet evaporation. Thus, flame struggles against the presence of water mist on the flame leading edge and either continues to propagate with almost the same velocity (as of without water mist), or complete extinction occurs. The extinguishing characteristics of fine water mist with the droplet diameter of the order of 30 microns are investigated. A critical concentrations of initial water mist mass fraction required for extinguishment have been achieved for the various conditions of flame spread phenomenon.