空气伴流条件下池火脉动特性研究

Study on the fluctuation characteristics of pool fire with air co-flow

通过实验与MATLAB程序对空气伴流条件下的池火脉动规律特性进行研究。结果表明:在空气伴流速度不超过0.15 m/s时,火焰脉动频率小,脉动振幅大,燃烧时间短;在空气伴流速度增加至0.19 m/s后,火焰投影面积和平均高度增加,火焰集中性大幅增强,脉动振幅大幅减小,火焰脉动频率增加,燃烧时间增加30%以上。通过实验发现脉动特性改变的主要原因是,在低空气伴流速度下油盘上方存在周期性脱落的旋涡;在高空气伴流条件下由于开尔文-亥姆霍兹效应减弱,漩涡消失,流线平滑波动小。

We combined the related experimental studies and MATLAB program to sludy the pool fire fluctuated characteristics under the air co-flow. The results showed that as the velocity of the air co-flow is nol bigger than 0.15 m/s, the flame fluctuation frequen cy is smaller, fluctualing amplitude is bigger, and the burnout time is shorter. When the velocity of the air co-flow in creased to 0.19 m/ s, the projected area, average height, and the centralization of flame increased, the fluctuation amplilude is highly reduced, the fluctuated frequency of flame increased. and the burnout time in creased beyond 30%. Experiments revealed that the main reason for the variation of the fluctuated characteristics is that at a lower air co-flow velocity the vortex is periodic shedding above the oil pan;at a higher air co-flow velocity, the Kelvin - Helmholtz effect was reduced. the vortexes disappeared. and then the smoother streamlines were instable decreased.