基于粗糙度的煤体表面接触角数值模拟研究

Numerical simulation of coal surface contact angle based on roughness

煤尘是煤矿的七大灾害之一,它不仅影响作业人员的身心健康,还能致使发生煤尘爆炸。煤的润湿效果对除尘有很大的影响,已有研究表明煤的润湿效果与煤的润湿性、表面粗糙度和表面活性剂等有关。为了有效地解决井下煤尘问题,选取了亲水性的哈密褐煤、疏水性的安阳焦煤和弱亲水性的赵固二矿无烟煤作为研究对象,使用光学接触角形貌联用仪测量3种煤样的均方粗糙度,测定3种煤样的本征接触角,利用COMSOL数值软件构建二维物理模型,设置模拟条件,调整模拟参数,分析对比试验值和模拟值,验证COMSOL数值模拟的可行性,研究了煤体表面粗糙度对煤体表面接触角的影响。结果表明:数值模拟的液滴铺展过程、液滴铺展速度及液滴铺展形态和试验情况类似,但模拟接触角值比试验接触角值大;随着煤体表面粗糙度的增加,褐煤接触角从60.7°降低到50.9°,变化范围在10°左右,焦煤接触角从96.5°增加到112.7°,变化范围在16°左右,无烟煤接触角从89.7°降低到78.3°,变化范围在11°左右;同种表面活性剂对3种煤样接触角的模拟值和试验值具有相同的变化趋势,但模拟值比试验值大。采用数值模拟的方法,研究煤体表面粗糙度对煤体表面接触角的影响具有一定的可行性。煤体表面受粗糙度影响的润湿情况符合Wenzel模型。表面活性剂的存在不改变3种煤样的接触角随表面粗糙度变化的规律。

Coal dust is one of the seven disasters in coal mine.It affects the health of workers and causes coal dust explosion.The wetting effect of coal has a great influence on dust removal.Studies have shown that the wetting effect of coal is related to the wettability,surface roughness and surfactants of coal.In order to effectively solve the problem of coal dust under the mines,which selects hydrophilic Hami lignite,hydrophobic Anyang coking coal and weakly hydrophilic anthracite of Zhaogu No.2 mine as the research objects.The mean square roughness of the three coal samples were measured by the optical contact angle morphology combined instrument,the intrinsic contact angles of the three coal samples were measured,the two-dimensional physical model was constructed by COMSOL numerical software,the simulation conditions were set,the simulation parameters were adjusted,the experimental and simulation values were analyzed and compared,the feasibility of COMSOL numerical simulation was verified,and the influence of coal surface roughness on coal surface contact angle was studied.The results show that the droplet spreading process,the droplet spreading velocity and the droplet spreading shape of numerical simulation are similar to those of experiment,but the simulated contact angle is larger than that of experiment.With the increase of coal surface roughness,the contact angle of lignite decreases from 60.7°to 50.9°,the variation range is about 10°,the contact angle of coking coal increases from 96.5°to 112.7°,the variation range is about 16°,and the contact angle of anthracite decreases from 89.7°to 78.3°,and the variation range is about 11°.The simulated and experimental values of contact angle of three kinds of coal samples with the same surfactant have the same change trend,but the simulated value is larger than the experimental value.It is feasible to study the influence of coal surface roughness on coal surface contact angle by numerical simulation.The wetting of coal surface affected by roughness conforms to Wenzel model.The existence of surfactant does not change the variation of contact angle with surface roughness of three coal samples.