干粉粒径对灭火器超声速气固两相流影响的数值模拟

Numerical simulation of the effect of dry powder particle size on supersonic gas-solid two-phase flow in the fire extinguisher

使用流体仿真软件FLUENT中的SST k-ω湍流模型与离散相模型对超声速喷管内外不同粒径气固两相流进行数值模拟,以研究干粉粒径对干粉灭火器灭火效能的影响。结果表明:随着干粉粒径的增大,马赫数等值线沿喷管轴线向下游推移,激波位置随之向下游变化,射流激波强度随颗粒粒径的增大而增大;1μm粒径气固两相流颗粒的随流性较强,颗粒速度受气相射流激波结构影响显著,在出口边界处颗粒分布较为分散;10、30、50μm粒径气固两相流颗粒速度分布不再受气相射流激波结构的影响,出口边界处颗粒分布集中性较高;在灭火火源目标的最佳距离处,10μm粒径气固两相流的颗粒喷射速度最大,使用10μm粒径干粉颗粒能够取得较好的灭火效果。该研究结果可为干粉灭火器颗粒粒径的选择提供参考。

The SST k-ω turbulence model and discrete phase model in the fluid simulation software FLUENT were used to numerically simulate the gas-solid two-phase flow with different particle sizes inside and outside the supersonic nozzle, with a view to explore the effect of dry powder particle size on the fire extinguishing efficiency of dry powder extinguisher. The results show that with the increase of dry powder particle size, the Mach number contour drifts downstream along the nozzle axis, and the position of shock wave moves downstream accordingly. The intensity of jet shock wave increases with the increase of particle size;gas-solid two-phase flow particles with a particle size of 1 μm have strong fluidity, and the particle velocity is significantly affected by the shock wave structure of the gas-phase jet, and the particle distribution at the exit boundary is relatively dispersed. The velocity distribution of gas-solid two-phase flow particles with a particle size of 10, 30 and 50 μm is no longer affected by the shock wave structure of the gas-phase jet, and the particle distribution at the exit boundary is highly concentrated. At the optimal distance from the target fire source, gas-solid two-phase flow particles with a particle size of 10 μm have the largest jet velocity, and dry powder particles with a particle size of 10 μm can achieve a good extinguishing effect. This result can provide a reference for the selection of particle size of dry powder fire extinguishers.