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    活性液滴碰撞浸润微细煤尘颗粒动力学特征模拟及实验研究

    Simulation and experimental study on the dynamic characteristics of active droplets colliding with and wetting fine coal dust particles

    • 摘要: 为探究活性液滴与微细煤尘颗粒碰撞过程中动力学特征及演化规律,以疏水性长治无烟煤为研究对象,通过测定表面粗糙度构建不同分形特征的非光滑球形颗粒模型。采用活性液滴浸润性能测定、煤样电镜扫描分析、液滴−煤尘颗粒碰撞实验及数值模拟相结合的研究方法,系统探究了活性液滴在煤尘颗粒表面动态润湿行为及作用机制。实验结果表明,经过对十二烷基苯磺酸钠、十二烷基硫酸钠、仲烷基磺酸钠和快渗T溶液的对比优选,质量浓度为0.03%的快渗T液滴表现出最优的润湿性能,其表面张力、接触角变化数值均下降到最低。经活性溶液处理的煤样,表面高度差相较于原煤样显著降低,其中由快渗T溶液处理后的煤样表面变化幅度最大,且生成多数垂直向贯通孔道结构,增大液滴的留存面积。通过活性液滴−颗粒碰撞实验发现,粒径比和相对碰撞速度是影响液滴在煤尘颗粒表面碰撞形态的主要参数,当液滴粒径比为1.5、碰撞速度为2.5~3.0 m/s时,液滴展现有效的包裹状态。模拟结果表明,煤尘颗粒表面粗糙度与液滴铺展行为存在显著关联。高粗糙度表面易引发应力集中现象,增加液滴破碎风险,而与活性液滴接触后表面粗糙度降低,利于液滴稳定铺展。液滴碰撞速度的提升可弥补液滴动能不足,且缓解因原煤表面强疏水性导致顶部界面处形成气膜层的问题。当碰撞速度提升至2.7 m/s时,活性液滴通过高速冲击快速填充表面微结构,并形成光滑的液−固过渡层,最终促使液滴达到完全铺展。

       

      Abstract: To investigate the dynamic characteristics and evolution of active droplets colliding with fine coal dust particles, hydrophobic Changzhi anthracite was taken as the research object, and non-smooth spherical particle models with different fractal characteristics were constructed based on measured surface roughness. A combined research methodology incorporating active droplet wettability testing, scanning electron microscopy (SEM) analysis of coal samples, active droplet–coal dust particle collision experiments, and COMSOL simulation was employed to systematically investigate the dynamic wetting behavior and collision mechanism of active droplets on coal dust particle surfaces. The experimental results show that among sodium dodecyl benzene sulfonate (SDBS), sodium dodecyl sulfate (SDS), secondary alkyl sulfonate (SAS), and KuaiShen T solution, the KuaiShen T droplet with a mass concentration of 0.03% exhibits the optimal wettability, with both surface tension and contact angle reduced to the lowest values. Compared with raw coal samples, coal samples treated with active solutions show a significant decrease in surface height difference. In particular, the coal surface modified by KuaiShen T solution displays the most substantial variation, forming numerous vertical through-pore structures that increase the retention area of droplets. Collision experiments between active droplets and particles reveal that the droplet-particle size ratio and relative collision velocity are the dominant parameters affecting the collision morphology of droplets on coal dust surfaces. Effective wrapping of particles by droplets is achieved at a size ratio of 1.5 and collision velocities ranging from 2.5 to 3.0 m/s. Numerical simulation results indicate a strong correlation between coal dust surface roughness and droplet spreading behavior. High surface roughness tends to cause stress concentration and increase the risk of droplet breakup, whereas the reduced roughness after contact with active droplets facilitates stable droplet spreading. Increasing the collision velocity compensates for insufficient droplet kinetic energy and alleviates the formation of an air film at the top interface caused by the strong hydrophobicity of raw coal. At a collision velocity of 2.7 m/s, active droplets rapidly fill the surface microstructures via high-speed impact, forming a smooth liquid-solid transition layer and ultimately achieving complete spreading.

       

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