基于FDS与CFD组合的快速烤燃数值模拟

Numerical Simulation of Fast Cook-off Based on the Combination of FDS and CFD

为了研究装填熔铸B炸药的试件在池火作用下的快速烤燃特性,采用火灾仿真软件FDS建立了池火燃烧模型;烤燃试件尺寸为Φ76mm×256mm,壁厚7.5mm,燃料为JP-8,计算了不同阶段的火焰结构特征和烤燃试件周围的温度变化;将试件不同位置的真实温度作为边界条件运用于CFD中,研究快速烤燃的特性及其参数,并将计算的响应时间、点火温度与试验结果进行了比较。结果表明,用FDS与CFD组合计算的快速烤燃温度—时间曲线与试验曲线吻合,最大误差为8.1%;获得了快速烤燃过程中火焰的辐射热通量与对流热通量的变化情况,辐射热通量占主导作用,占比为总热通量的91%左右;得到了快速烤燃的池火燃烧特性以及油池与烤燃试件尺寸的匹配关系,油池尺寸越大,火焰温度越高,池火发展阶段的时间缩短,辐射热通量占比增大到95%;B炸药发生点火时,表层达到熔化的炸药极少,药柱内部温度仍为常温,点火区域在试件端面棱角处。

A pool fire combustion model was established by the fire simulation software FDS to study the fast cook-off characteristics of the test specimen filled with casting composition B in the pool fire.The test specimen isΦ76mm×256mm with a wall thickness of 7.5mm,and the fuel is JP-8.The structural characteristics of the flame in different stages and the temperature variations around the test specimen were calculated.The real temperatures at different positions of the test specimen were the boundary conditions in CFD to study the characteristics and parameters of the fast cook-off.The calculated response time and ignition temperature were compared with the test results.The results show that the temperature-time curve calculated by the combination of FDS and CFD is consistent with the experimental curve and the maximum error is 8.1%.The changes of flame radiative heat flux and convective heat flux are obtained,and the radiative heat flux plays a dominant role,accounting for about 91%of the total heat flux.The combustion characteristics of the fast cook-off pool fire and the size relations between the oil pool and the test specimen were summarized.The larger the size of the oil pool is,the higher the flame temperature is,the shorter the development of the pool fire is,and the proportion of radiant heat flux increases to 95%.When composition B is ignited,very few surface explosives melt,the inside of the charge column is still at the initial temperature,and the ignition area is at the corners of the test specimen section.