在绝热流动情况下非球形水滴的运动特性

采用非球形颗粒的阻力系数关联式，建立了水滴在绝热逆流空气中的动力学方程，得出了水滴所受阻力及其最终沉降速度的计算方法。在此基础上，分析了水滴变形程度和内部流动对水滴运动特性的影响，结果表明水滴变形程度增加使得水滴受到的空气阻力增大，而最终沉降速度减小，水滴的内部流动导致其受到的空气阻力减小，计算条件下最大偏差可达15％。     

剪切流场中分散相液滴内外流场静压差研究

目前,在乳化液破乳机理研究中,剪切流场作用下分散相液滴行为的研究因流场复杂性及测量技术的局限性,对变形前后液滴内外流场静压差的了解非常有限,并多假设其在变形过程中保持恒定或变化不大。针对这一问题,通过改进设计内外桶反向旋转剪切实验装置,结合数字图像处理技术,设计了一种较为精确的液滴内外压差测量方法。从实验角度率先研究了液滴变形过程中内外压差变化规律,数据结果显示液滴变形过程中内外压差变化显著,且影响液滴形态变化,内外压差随剪切速率及液滴综合变形度单调递增。分析表明,对于剪切流场中液滴形变模型的建立及数值模拟相关研究,需考虑过程中存在的液滴内外压差变动因素。     

黏性流体的二次雾化特性

 针对渣油沥青气化工艺,以高温下渣油沥青的雾化为研究背景,选择与其物性相近的甘油水溶液作为模拟介质,进行了黏性液体二次雾化的实验。利用高速摄像仪和图像处理软件,对单个液滴在不同条件下的破裂模式、特征尺度、破裂时间和破裂后的平均液滴直径等进行了观察和分析。结果表明,随着韦伯数(We)的增加,甘油液滴的破裂依次呈现5种不同的模式：袋状破裂、袋状-雄蕊破裂、双重袋状破裂、剪切破裂和爆发式破裂。在低 We 下,液滴直径最大变形率基本相同;在高 We 下,总破裂时间明显缩短,破裂产生的液滴粒径很小,雾化效果良好。     

降低MTBE产品硫含量的探讨

对国内炼油厂MTBE总硫含量偏高的原因进行了分析.指出液化石油气脱硫醇过程中产生的RSSR(二硫化物)液滴直径小、与碱液的密度差小,且碱液的黏度较高,这些因素使RSSR无法仅靠重力作用从碱液中脱除,在碱液循环过程中又被反抽提至液化石油气中,造成液化石油气总硫含量超标.另外,MTBE装置催化剂的磺酸基团脱落也会造成MTB...     

用格子Boltzmann方法模拟液滴合并过程

用格子Boltzmann方法中的伪势模型对两个液滴的合并过程进行了数值模拟。详细研究了两液滴能否合并临界尺寸和液滴合并过程中液桥的形成与演化的关系，并研究了表面张力对合并速度的影响。研究结果发现当两个液滴之间距离小于2倍界面厚度时，两个液滴在不受外力的作用下能够自动合并；液桥的宽度与演化时间有一定的指数关系；表面张力越大，合并速度越快，这个结果与前人的理论预测和实验结果一致。     

Effects of liquid viscosity on inception of disturbance waves and droplets in gas–liquid annular two‐phase flow

The structure of gas–liquid two‐phase flow is investigated in order to establish a reliable criterion for the development of disturbance waves and droplets considering the effects of liquid viscosity. The structure of the gas–liquid interface and the flow rate of droplets entrained in gas are measured simultaneously at five kinematic viscosities (1.0, 3.2, 9.9, 30, 70 mm²/s). The time‐series traces of liquid film thickness measured by five holdup probes reveal that the inception of disturbance waves occurs at a liquid Reynolds number of 200 or a non‐dimensional liquid film thickness of 6.5. It is also shown that droplets are generated before the inception of disturbance waves with increasing liquid kinematic viscosity at a liquid velocity of 0.02 to 0.03 m/s. As previously published criteria for the inception of droplets are found to be unsatisfactory, a new critical condition for droplet generation balancing the interfacial shear stress $τi$ with the wave height h and surface tension σ is proposed: $τih/σ=0.025$. This relation describes the action of shear force and surface tension on wave crests, and is notably independent of liquid viscosity. © 2007 Wiley Periodicals, Inc. Heat Trans Asian Res, 36(8): 529–541, 2007; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/htj.20176     

Development of a Flat‐Plate Cooling Device for Electronic Packaging

In this study, a microcapillary pumped loop (MCPL) that can be used as a cooling device for small electronic and telecommunications equipment has been developed. For thin devices such as an MCPL, securing a vapor flow space is a critical issue for enhancing the thermal performance. In this letter, such enhancement in thermal performance was accomplished by eliminating condensed droplets from the vapor line. By fabricating the grooves in the vapor line to eliminate droplets, a decrease in thermal resistance of about 63.7% was achieved.     

Scanning droplet cell investigations on single grains of a FeAlCr light weight ferritic steel

Polycrystalline Fe7.5Al7Cr is a ferritic light weight steel that shows a strong anisotropic dissolution behaviour. This electrochemical phenomenon was investigated by use of a scanning droplet cell (SDC). The crystallographic orientation of the single grains was determined by electron back scatter diffraction (EBSD). The fraction of grains with a near 〈1 1 1〉 orientation (<10°) was 1.88 times higher than that of the near 〈0 0 1〉 orientation prior to annealing and 3.58 times higher after annealing. Voltammograms were performed on single grains with low index planes. The critical current density was 53% higher on 〈0 0 1〉 grains as compared to 〈1 1 1〉 grains. These results are used to discuss the electrochemical behaviour of the polycrystalline FeAlCr.     

Prediction of the size distribution of secondary ejected droplets by crown splashing of droplets impinging on a solid wall

Crown splashing is frequently observed during the impact of a droplet on a rough or wet wall. The size distribution of secondary ejected droplets has been experimentally observed to satisfy the log–normal distribution which contains two free parameters: the most probable diameter d_s and the width of the distribution γ. The most probable diameter will be determined through a simplified physical analysis. The width of distribution will be determined by using the principle of maximum rate of entropy production. The theory, containing no free parameters, predicts known experimental results with an acceptable engineering accuracy, provided the Froude number is high enough.     

油/聚合物溶液体系动态界面扩张模量的测量

以十二烷为油相,以HPAMMo 4000(M=2.0×107,HD=24%)在0.5%NaCl盐水中的溶液为水相,用法国ITConcept公司的Tracker型全自动液滴界面张力仪在30℃测定了油水界面的动态扩张模量E。结果表明,初始滴体积V对E～t曲线无明显影响;固定V=20μL,E达到动态平衡值所需时间(振荡周期λ=10s)随水相聚合物浓度CP增大而缩短,E平衡值随CP增大而增大,随λ增大而略有减小,因此V,t,λ等测量参数均需采用实验方法确定。根据纯水表面张力测量值,此方法的实验误差为0.7%。介绍了测量原理。用此法测定胜利孤岛原油(70℃粘度52.9mPa·s)与0.75、1.0、1.5g/LMo 4000溶液间的E值,分别为16.4、17.8、21.4mN/m。图3表2参7。