不同变质程度煤体表面液滴铺展特性实验研究

Experimental study on the spreading characteristics of liquid droplets on coal surfaces with different degrees of metamorphism

为研究不同变质程度煤体表面液滴铺展特性,采用实验与数值计算相结合的方法,通过观察纯水液滴撞击煤体的动态铺展过程,探讨撞击高度对不同变质程度煤表面接触角及液滴铺展系数的影响,揭示不同变质程度煤体的润湿机理。测量4种不同煤质的静态接触角,实验结果表明:褐煤的润湿性最强,肥煤次之,无烟煤和焦煤的润湿性最差;观察纯水液滴碰撞不同煤样的动态变化发现,撞击高度与纯水液滴的铺展系数之间存在正相关关系;在相同高度下,纯水液滴铺展系数的变化均表现为先增大后降低再增大,最终趋于一个稳定状态。该研究结果可为矿井湿式除尘技术提供一定的理论参考。

[Objective]This study investigates the influence of droplet impact height on the spreading characteristics of liquid droplets on coal surfaces with different degrees of metamorphism.The study also explores the surface reaction mechanism and adsorption behavior of coal when subjected to droplet impact.The dynamic interactions between water droplets and coal surfaces are crucial for enhancing the effectiveness of spray dust reduction in coal mines.This research reveals the characteristics of coals with different degrees of metamorphism when exposed to water mist,providing a theoretical basis for improving the working environment of coal miners,reducing coal dust pollution,and mitigating explosion risks.[Methods]The dynamic spreading process of pure water droplets impacting different coal samples from different heights was examined using high-speed video cameras,contact angle measurement instruments,and piezometers.Experiments and numerical calculations were used to explore the effects of impact height on the contact angle and spreading coefficient of pure water droplets on coal surfaces with varying degrees of metamorphism.The wetting mechanism of coal bodies with different degrees of metamorphism and the changing pattern of the impact of the pure water droplets on coal bodies with different degrees of metamorphism was analyzed from both macro and microscopic perspectives.[Results]The experimental results show that upon impacting four coal samples with different degrees of metamorphism,water droplets initially spread rapidly from the collision center to the periphery.After reaching the maximum contact area with the coal surface,the droplets began to retract toward the center,achieving the maximum retraction height before settling into a steady state following continuous oscillation and eventually lying flat on the surface of the coal sample.The effect of deterioration on the coal-water contact angle was observed at consistent impact heights.The contact angle between coal and pure water first increased and then decreased as the degree of coal metamorphism progressed.[Conclusions]Among the four coal samples tested,lignite exhibited the strongest wetting ability,followed by fat coal,while coking coal and anthracite showed the weakest wetting ability.The study also observed the variation in the spreading diameter of pure water droplets on coal surfaces at different impact heights.The spreading coefficient of the droplets increased with increasing droplet impact height.Variations in the spreading diameter of pure water droplets on the coal surfaces at different impact heights were observed.As the contact time between the droplet and the coal surface increased,the spreading coefficient first increased,then decreased,increased again,and finally stabilized.In addition,at the same impact height,the time required for coal samples with different degrees of metamorphism to reach the maximum spreading coefficient was consistent.These research results provide a theoretical reference for the development and application of coal mine water mist dedusting technology,thereby ensuring safer coal mine production.