基于大涡模拟的油池火焰瞬态辐射传热研究

Transient radiative heat transfer of pool fires based on large eddy simulation

为探究油池火焰燃烧过程中火焰辐射的瞬态辐射传热特性,基于大涡模拟方法建立甲醇油池火焰的燃烧模型,并采用准确性高的灰气体加权和模型(WSGG)模拟高温气体非灰辐射特性;研究甲醇火焰瞬态燃烧过程中的温度、速度、组分浓度变化及辐射热量的瞬态分布特性。结果表明:燃烧气体温度呈现周期性的变化,会不断地有高温气体在油池表面生成,然后上升、膨胀扩散,且在上升过程中气体速度先变大后减小。受此影响,池火液面受到的辐射热反馈随时间剧烈震荡,液面中心辐射热流密度在-17~-7 kW/m^(2)之间变化,且向液面边缘逐渐减小;液面的热流密度概率密度分布呈现三角形;地面的辐射热量因为距离火焰较远及油罐的遮挡作用,比液面小一个数量级。

In order to explore transient radiative heat transfer characteristics of pool fires,a combustion model of methanol fire was developed based on large eddy simulation,and non-gray radiative properties of combustion gases were simulated by adopting accurate weighted sum of gray gases(WSGG)model.Then,transient characteristics of temperature,velocity,species concentration and radiative energy were investigated.The results show that gas temperature varies in a periodical pattern,during which high temperature gases form above pool surface,then rises,expands and spreads in cycles,with its velocity increasing first and then decreasing during rising process.Due to this factor,radiative feedback at surface shows an oscillating behavior,and radiative heat flux at center varies between-17 and-7 kW/m^(2) drastically,which decreases along radial direction.Moreover,probability density of heat fluxes at surface spreads like a triangle.As the ground is far away from fire and partially blocked by tanks,its heat flux is one order of magnitude smaller that of pool surfaces.