微米尺度下雾滴与尘粒碰撞后液体附着特性研究

Characterisation of liquid residue after collision between droplets and dust particles at micron scale

  • 摘要: 粉尘易引发爆炸事故和人员尘肺病,水雾是应用最广泛的降尘介质,但由于对尘−雾接触后的附着状态缺乏科学认识,喷雾降尘率增长面临瓶颈。通过数值模拟和实验方法,研究了微米尺度下的雾滴−尘粒碰撞行为,得出了尘粒表面液体附着量与4类碰撞行为之间的关系。研究结果显示,降低雾滴表面张力和接触角在低速碰撞有利于避免“反弹”行为发生,也有利于在“膜状飞溅”行为发生时增大尘粒表面的液体附着量。但是,降低雾滴表面张力和接触角也会降低雾滴发生破裂的临界碰撞速度,导致发生“完整并聚”行为的速度范围缩小,对降尘效果有不利影响。同时,还发现降低雾滴粒径和增大雾滴黏度均有利于增大尘−雾碰撞过程中黏性摩擦损失,从而抑制“反弹”行为和雾滴破裂现象发生,有利于增大尘−雾作用后尘粒表面的液体附着量,含0.329%质量分数高分子成分R1001的液滴连续碰撞固体颗粒时,颗粒表面液体残留量比纯水液滴碰撞的情况可提高至少10倍,所以在水中添加增稠成分可显著提升粉尘增重、沉降效果。上述发现可为新型降尘剂开发提供新思路,也可为喷雾降尘工况参数优化提供理论支撑。

     

    Abstract: Dust easily triggers explosion accidents and occupational pneumoconiosis. Water mist is the most widely used dust suppression medium. However, due to the lack of scientific understanding of the adhesion state after dust-mist contact, the growth of mist dust suppression rate is facing bottlenecks. Through numerical simulation and experimental methods, the collision behavior of micrometer-scale droplet-dust particle was studied, and the relationship between the liquid adhesion amount on the dust particle surface and four types of collision behavior was obtained. The research results show that reducing the surface tension and contact angle of the mist droplets is beneficial to avoiding “rebound” behavior in low-speed collisions and also increases the liquid residue on the dust particle surface when “membrane splashing” behavior occurs. However, reducing the surface tension and contact angle of the mist droplets also lowers the critical collision velocity at which mist droplets rupture, resulting in a narrower range of speeds for “complete coalescence” behavior, which has a negative impact on dust suppression. This study also found that reducing the mist droplet size and increasing the mist droplet viscosity are both beneficial for increasing the viscous friction loss during the dust-mist collision process, thereby inhibiting “rebound” behavior and mist droplet rupture, and increasing the liquid adhesion amount on the dust particle surface after dust-mist interaction, significantly improving dust weight gain and settling effects. These findings can provide new ideas for the development of new dust suppressants and theoretical support for the optimization of spray dust suppression operating parameters.

     

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