为了能更真实反映变截面硅微通道内惯性力驱动水银微液滴的流动特性,在数值仿真中应考虑接触角滞后对流动特性的影响。利用FLUENT软件的VOF-CSF模型研究了惯性微流体开关中水银微液滴在变截面微通道内受惯性力驱动的流动特性,编写动态和静态接触角滞后的UDF函数,对变截面微通道中内流动特性进行了数值仿真分析。结果表明,设置静态接触角和加载10°接触角滞后UDF函数时,惯性微流体开关的加速度阈值分别为13.2 g n和16.4 g n。不同接触角滞后值对水银微液滴的流动特性有重要影响,且接触角滞后性越大,水银液滴流动速度降低,更难冲破微阀进入储液槽。由于水银液滴在惯性力驱动下的接触线运动速度较低,动态接触角对流动特性的影响可以忽略,动态接触角滞后可由静态接触角滞后代替。

In order to truly reflect the flow characteristics of mercury droplet flow in varying-cross-section microchannel driven by inertia force, the impact of contact angle hysteresis on flow characteristics should be considered in numerical simulations. The VOF-CSF model of FLUENT software is used to study the flow characteristics of mercury droplet flow in varying-cross-section microchannel of micro fluidic inertia switch. Write the UDF of dynamic and static contact angle hysteresis,and simulate the flow characteristics in varying-section-mi-crochannel. The results show that the static contact angle and the contact angle hystersis of 10oare set in simulation, the acceleration threshold of micro fluidic inertia switch is 13. 2 gn and 16. 4 gn,respectively. The different contact angle hysteresis have an important impact on flow characteristics. The greater the contact angle hysteresis, the smaller the flow velocity of mercury droplet, and the harder mercury droplet breaks through the micro-va

矿井喷雾降尘是利用水雾使粉尘润湿沉降的过程，考虑到固体与液体间分子作用力，本文采用格子Boltzmann方法对液滴沿固壁铺展的动力学行为进行了数值模拟，结果发现铺展直径及动态接触角随时间呈指数规律，确定了液滴表面张力与铺展最大直径间的关系，固壁润湿性对铺展最大速度值影响较大，这些与物理试验及文献结果符合良好。进一步考察了疏水性强的固壁，发现当液滴表面张力足够小时，铺展接触角可以在90?以下，与理论公式符合。研究发现铺展过程中伴随着振荡，且铺展到最大时液膜有回缩趋势。

Spray dust mechanism is to use spray to wet and reduce the coal mine dust. Based on lattice Boltzmann method, the dynamic behaviors of droplet spreading on solid surface are simulated numerically in consideration of the molecules reaction between fluid and solid. Results show that the spreading diameter and dynamic contact angle change exponentially with time. The relationship between droplet surface tension and maximum spreading diameter is determined;it is shown that the wettability of solid surface has a great influence on the maximum spreading velocity. All the above numerical results are in good agreement with the experimental and theoretical results reported in the literature. Moreover, the solid surface with high hydrophobicity is further investigated. It is found that the spreading contact angle can be less than 90?if the droplet surface tension is small enough, which agrees well with the theoretical formula. The simulation also shows that there occurs oscillations in the sprea

采用淬火法对质量分数为0.002%的氧化石墨烯水悬浮液的瞬态沸腾特性进行了表征。通过对三种代表性工况的对比分析研究了氧化石墨烯在沸腾表面的沉积对淬火沸腾过程的影响。由于氧化石墨烯在过渡沸腾阶段的沉积,水悬浮液的淬火过程较之去离子水缩短了约10 s,临界热通量则提升了约10%,对应的表面接触角从104°减小到78°。将已沉积表面再次在去离子水中淬火后,表面接触角回升到89°,临界热通量则有所回落。结果表明,氧化石墨烯的表面沉积虽然是强化临界热通量的决定性因素,但淬火过程的速率和过渡沸腾阶段的传热速率还受到氧化石墨烯的动态沉积过程和水悬浮液中悬浮氧化石墨烯的共同影响。

The transient boiling of an aqueous suspension with graphene oxide nanosheets (GONs), at a mass fraction of 0.002%, was characterized using the quenching method. The effects of GONs deposited on the boiling surface were compared among three representative cases. With the deposition of GONs during the transition boiling phase, the quenching period of the suspension was shortened by 10 s as compared to that of deionized water, while the critical heat flux (CHF) was improved by 10%and the contact angle was reduced from 104° to 78°. After subsequent quenching of the boiling surface with GON deposition in deionized water, the contact angle was increased to 89° and the CHF was somewhat deteriorated. It was concluded that the enhancement of CHF is primarily resulted from surface deposition of GONs. The quenching speed and the heat transfer rate during the transition boiling phase are also affected by the dynamic deposition process and the suspended GONs.

输电线路是否更换运行中的复合绝缘子需要客观、准确、快速、方便地评判出该复合绝缘子的憎水等级。在提出评判工作的标准后，对国内外憎水等级评判工作进行综述，总结了复合绝缘子憎水等级评判的研究现状。首先。对接触角法、喷水分级法以及表面张力法等几种传统的评判方法进行总结比较，并指出由于动态接触角法能够客观准确地评判出复合绝缘子的憎水等级，该法将广泛地利用于憎水等级评价工作中，尽管目前没有利用于憎水等级的在线评判。其次，对基于数字图像处理的憎水等级评判方法的过程进行总结，针对各个过程国内外所采取的方法进行比较、总结。最后，提出实现多因素多参量评判复合绝缘子憎水等级评判是今后工作的发展方向。

@@@@The current evaluation methods for hydrophobic nature of the composite insulators are summarized , including the basic evaluation methods, that is, the contact angle method, water spray classification and surface tension method , and the classification methods of hydrophobic nature based on digital image processing .The processes of classification methods of hy-drophobic nature based on digital image processing are emphatically discussed and compared as well as the advantages and dis -advantages of the adopted methods used in each process .In order to realize the on-line evaluation for hydrophobic nature of composite insulators objectively, accurately, rapidly and conveniently , some suggestions on using the dynamic contact angle to evaluate the hydrophobic nature of composite insulators on line are proposed .At last, it is put forward that using the multi -factor and multi-parameter to evaluate the hydrophobic nature of composite insulator is the development direction of the futur

采用烯基琥珀酸酐(ASA)对瓜尔胶原粉进行改性来制备一种环境友好型表面施胶剂,对纸张进行表面施胶并对其施胶效果进行了测定。讨论了瓜尔胶与ASA的用量比例、反应温度及反应时间等对施胶效果的影响,同时采用红外光谱(FT-IR)、X射线衍射(XRD)和动态接触角(DCA)等测试手段对其结构、性能和应用效果进行了表征。结果表明,当瓜尔胶原粉与ASA比例为7:1,反应温度为60℃,反应时间为10h,在瓜尔胶分子上成功引入疏水性长链,改性瓜尔胶表面施胶浓度为2.5%时,纸张的施胶度可以达到54s,动态接触角可达118°以上。

In order to prepare a kind of environment-friendly surface sizing agent, the guar gum was modified by alkenyl succinic anhydride （ASA）, and the surface sizing effect of the modified guar gum was studied. ~ae effect on surface sizing of the reactant ratio, reaction temperature and reaction time were discussed, and the structure, performance and application effect were characterized by the infrared spectrum （FT-IR）, X-ray diffraction （XRD）, dynamic contact angle （DCA） and so on. ]-he results showed that when the ratio of the guar gum and ASA was 7：1, reaction temperature was 60~C, reaction time was 10 hours, the hydrophobic long chain was introduced onto the guar gum successfiaUy. As the dosage of modified guar gum was 2.5%, the sizing degree was up to 54 seconds, and the dynamic contact angle was more than 118°.