辊式涂布两辊间隙施涂过程的数值计算分析

目的系统地计算涂层厚度与两辊间隙、涂布辊速度以及胶黏剂的流体稠度和流动指数等影响因子的关系。方法在分析该复杂流动机理的基础上,利用CFD软件对具有非牛顿流体特性胶黏剂的两辊间隙施涂过程进行二维数值模拟。结果在五辊无溶剂涂布工程中,两辊间隙增大,最终涂布厚度也明显增大;增大涂布辊转速,涂布厚度也将减小;胶黏剂的流体稠度越大,最终传递到基材上的涂层厚度减小。结论两辊间隙的大小对涂层厚度的影响最大,胶黏剂的流体稠度、流动指数也对涂层厚度有较大的影响。     

五辊无溶剂涂布涂层厚度数学模型与影响因子分析

目的研究如何实现高效的无溶剂涂布,获得稳定的预定厚度涂层。方法在建立两辊间隙间涂布液流动数学模型的基础上,从涂布液辊间间隙分流分配关系和总结构内涂布液流量平衡两方面,分析无溶剂五辊顺转涂布系统涂布厚度的影响因素。结果转移钢辊和涂布钢辊的速比,计量辊和转移钢辊之间的间隙以及橡胶转移辊的压力等是对涂层厚度有直接影响的因子,毛细准数是涂层竖条道缺陷的主要影响因子,而涂布液的非牛顿特性会加重竖条道缺陷。结论设计无溶剂五辊顺转涂布系统时,需要综合考虑辊的直径、施加给橡胶辊载荷大小的范围、橡胶辊的硬度、适用涂布液的粘度范围和速度极限等因素。     

薄膜运动速度对夹带气体流场特性的影响

目的研究不同运动速度下薄膜和导向辊之间夹带气体的流场特性。方法分析薄膜和导向辊的运动特点及它们之间夹带气体的形成机理,完成夹带气体流场的理论建模。对运动薄膜和导向辊之间夹带气体的流场进行数值模拟,结合工程实际情况分析讨论流场特性随薄膜运动速度的变化规律。结果随着薄膜运动速度的增加,空气夹带量随之增加,楔形入口区域内流体的流动速度分布范围变大,在包角出口区域流体流出的速度增加,流程变大。结论薄膜运动速度是影响夹带气体流场特性的主要因素,夹带气体在入口区域形成局部涡流,涡流会导致流体运动状态不稳定,进而引起薄膜产生振动。     

真空导入模塑工艺纤维预成型体厚度变化和流体压力变化研究进展

纤维预成型体厚度控制问题是真空导入模塑工艺(Vacuum infusion molding process,VIMP)面临的主要挑战之一。综述了国内外关于纤维预成型体压实回弹特性和渗透率特性的研究进展,介绍了VIMP工艺在一维线性流动和二维径向流动时厚度变化的理论模型,分析了流体压力特性方程的求解、流体压力场的分布和流体压力对厚度的影响,指出了Correia推导过程中存在的问题并进行了修正,总结了厚度变化对VIMP工艺及复合材料制品的影响,并对VIMP工艺厚度变化的理论研究和工艺控制进行了展望。     

浸辊涂布涂层厚度在线检测平台的机理建模与设计

目的研究实际涂布生产中涂层厚度的在线监测方法。方法以非牛顿流体为基础,对浸辊涂布过程进行数学推导和理论分析。结果小型浸辊涂布的涂布头实验平台可对涂布液转移过程中形成的弯月面以及浸辊上的涂层厚度进行图像分析处理。结论设计出了可以实时在线监控涂布设备的涂层厚度及质量的实验平台,能较好地应用在实际生产中。     

基于 SOLIDWORKS 与 ADAMS 的瓦楞辊动力学仿真

运用 SOLIDWORKS 优秀的建模功能和 ADAMS 的动力学仿真功能,对瓦楞辊运动过程进行了建模仿真。利用 ADAMS 中的 IMPACT 函数对辊齿间的接触进行定义,通过 Hertz 弹性碰撞理论确定了 IMPACT 函数中的各参数。 从仿真结果中得出了瓦楞辊运动啮合时中心距的变化曲线,从而分析了瓦楞辊的运动过程对瓦楞纸芯成形质量产生的影响。     

基于Ansys的锂电池极片辊压质量改善研究

目的 优化辊压机结构,减小辊压后极片的不均匀性,进一步提升锂电池性能。方法 首先,将辊压机工程模型简化为仿真模型,运用Hypermesh对仿真模型进行网格划分,重点加密极片和轧辊接触区域的网格,将划分好的网格以Inp格式导入Ansys中,设置边界条件并求解计算,模拟轧辊辊压极片的过程。其次,提取极片监测点的仿真数据,换算得到极片辊压后的厚度,将仿真结果与实验数据对比,验证极片辊压仿真方法的准确性。最后,运用该仿真方法分析液压弯缸力、弧形辊弓高和轧辊辊面长度等对极片辊压质量的影响。结果 分析仿真和实验结果可知,辊压后极片的厚度平均值和极差值对标率均在90%以上,证明了仿真方法准确可靠。随着弯缸力(0~784 000 N)逐渐增大,极片厚度极差值先减小后增大;随着弧形辊弓高(0~60 μm)逐渐增大,极片厚度极差值先减小后增大;随着轧辊辊面长度(1 200~1 500 mm)逐渐减小,极片厚度极差值逐渐减小。结论 施加合适的弯缸力、对弧形辊进行设计均可改善极片辊压质量。轧辊辊面长度越小,极片辊压效果越好。可通过极片辊压仿真方法确定最优弯缸力大小与弧形辊最优弓高,该方法大幅度缩短了辊压机研发周期,优化了辊压机性能,提高了极片辊压质量,为锂电池性能的提升奠定了基础。     

基于有限元分析的瓦楞辊中凸曲线优化设计

目的研究瓦楞辊在复杂工作应力条件下的中凸度优化设计。方法通过理论力学的方法,建立相应的上、下瓦楞辊的中凸度数学模型,推导出中凸曲线方程。对优化后的瓦楞辊进行力的加载和几何约束等边界条件,建立有限元模型,并且使用Ansys软件进行模拟仿真,将优化前后的中凸值和6对啮合的瓦楞辊间隙值进行比较。结果优化后的上瓦楞辊中凸值比优化前最大降低了31.1%,下瓦楞辊中凸值比优化前最大降低了43.7%;6组啮合的瓦楞辊,优化后比优化前的中凸值间隙减小,说明优化后的6组瓦楞辊的自身受力情况较为均匀,生产出的瓦楞纸板质量更好,并且瓦楞辊之间的阻力减小,延长了瓦楞辊使用寿命。结论通过对瓦楞辊中凸曲线进行优化设计,将上瓦楞辊制成向下凹的形状,同时将下瓦楞辊制成向上凸的形状,根据有限元仿真的数据对比得出研究方法是合理可靠的。     

轮胎辊与锥辊立磨粉磨过程力学分析

为了对立磨中轮胎型和锥型磨辊的粉磨过程进行分析比较,运用微分剪切理论建立轮胎型与锥型磨辊研磨物料的数学模型:通过建立磨辊-物料接触区域不同位置料层厚度的数学公式,得出料层微分单元受力的平衡方程;将方程积分得到磨辊与物料接触力及接触面积的大小。通过计算,得出在研磨过程不同参数(料层厚度、工作压力以及磨辊偏角)与接触面积之间的关系,并对2种磨辊进行比较分析。结果表明:磨辊偏转角度越大,磨辊所受应力峰值越大;在相同工作条件下,轮胎辊与物料有更大的接触面积,较小的应力峰值。     

双出杆液压减振器高频特性模型研究

为准确反映液压减振器在高频激励下的输出特性,基于流体惯性和局部流动损失等因素对阻尼液流动的影响规律,结合高频激励下减振器阻尼间隙内的流动特征,建立能够准确反映液压减振器高频动态特性的动力学模型,对液压减振器产生的阻尼力进行理论预测研究。试验与仿真分析结果均验证了该模型的准确性。     

涂料对消失模铸造金属液充型过程影响的数值计算

采用数值模拟技术研究了料对消失模铸造金属液充型过程的影响，结果表明，涂料透气性与涂料最度严重影响金属液的充型速度以及金属液－模样间隙压力和间隙宽度大小。     

涂布技术研究进展

综述了压辊类涂布、刮刀类涂布、挤出涂布、帘式涂布、旋转涂布和喷雾涂布等涂布技术的特点。指出了选择合适的涂布方式、加强涂层在线检测控制和调整涂布液流变特性,是涂布技术向更快、更精发展的重要手段。     

Bioinspired Anti-Plateau–Rayleigh-Instability on Dual Parallel Fibers

The Plateau–Rayleigh instability (PRI) is a well-known phenomenon where a liquid column always breaks up into droplets to achieve the minimization of surface energy. It normally leads to the non-uniformity of a liquid film, which, however, is unfavorable for the fluid coating process. So far, strategies to overcome this instability rely on either the surfactants, UV/high-temp curing treatments, or specific chemical reactions, which suffer from both limited liquid composition and complicated experimental conditions. Natural mulberry silk, a typical composite fiber, is produced by silkworms through a similar fluidic coating process, but exhibits a remarkably uniform and smooth surface. Drawing inspiration, it is revealed that the unique dual parallel fibers are capable of overcoming the PRI during the fluid coating process. Such anti-PRI ability is attributable to the changes in the Laplace pressure difference caused by the alternative asymmetry of the liquid film, as has been demonstrated by both a force analysis on the irregular liquid film and theoretical simulation according to the stability of the liquid on parallel fibers in the fluid coating process. The strategy is applicable for preparing various smooth functional coatings on fibers, which offers new perspectives for fluid coating and microfluidic technologies.     

Optimization of slot-coating processes: minimizing the amplitude of film-thickness oscillation

Slot coating is one of the most common coating methods for high-precision coatings. The flow limits of steady-state operation have been extensively analyzed in the literature. However, even the best-designed slot-coating operations are subjected to small oscillations on process conditions, such as flow rate, vacuum pressure and gap fluctuations. These time-dependent events lead to thickness variations on the deposited liquid layer that may be unacceptable for product performance. Therefore, the design of slot-coating processes, e.g. the specification of process conditions and die geometry, has to take into account not only the behavior of steady-state flow but also how the flow responds to small periodic disturbances. The process parameters should be such that the film-thickness oscillation is minimized. In this study, coating-thickness variations related to an ongoing oscillation of the coating gap is studied for different process parameters and frequency of the perturbation by solving the transient Navier–Stokes equations with appropriate boundary conditions for free-surface flow. The amplitude of the deposited film-thickness oscillation is used as the objective function of a bound-constrained optimization algorithm. The results show that at a fixed web speed and wet thickness, the film-thickness amplitude may be reduced by a factor of 4 by adjusting other process parameters.     

Local heating effect on film flow structure

Studies of fundamental regularities governing film flow regimes are of interest for wide range of practical problems appearing in projecting and optimization of technological plants in energetic, chemical industry and other branches of industry, including space technologies. The present work is devoted to theoretical study and numerical modeling of processes in film flow of fluid on inclined surface with local heat source. Experimental researches carried out at the Institute of Thermophysics SB RAS [1] show that the effect of thermocapillarity under certain conditions can significantly influence the regime of film flow. Forming of “roller” of fluid is observed in the experiments in the area with high gradient of film surface temperature. If the temperature (or surface tension) gradient exceeds certain critical level then the periodical 3-D flow structure appears. The main quantity of fluid is gathered in periodical streams (or “fingers”). Between the streams the thickness of film decreases significantly [2]. The authors’ previous theoretical results described 2-D regime of locally heated film flow [3, 4, 5]. Those results allow us to state the following hypothesis: 2-D flow structure becomes unstable and 3-D perturbations grow as the local arrest of liquid is achieved due to thermocapillary effect (in the frame of reference moving with the heat source) [6, 7]. The results of linear stability analysis and numerical modelling are presented.     

热镀锌过程挡板对镀层均匀性影响的模拟研究

为解决热镀锌过程中常出现的边部过镀锌缺陷,利用数值模拟方法对热镀锌气刀射流喷吹过程进行仿真研究,分析了挡板厚度对带钢边部压力场的影响;并借助镀层厚度计算模型,计算挡板厚度和边部角度对镀层厚度的作用关系;同时通过不同拉钢速度、气刀狭缝总压等工况,对挡板的厚度及边部角度进行优化.结果表明:随挡板厚度减小,带钢边部作用力增大并逐渐接近中心处;带钢边部镀层厚度随挡板厚度的减小而变薄,随挡板边部角度的增加而先减小后增大;挡板厚度2 mm、边部角度90°时,能有效提高带钢横向作用力和镀层分布的均匀性.     

Evaluation of the Loss of Propylene Glycol During Aqueous Film Coating

A Plackett-Burman study was used to determine the coating factors which can affect the loss of propylene glycol, a common water soluble plasticizer used in aqueous film coating, during the film coating process. The processing variables studied were: application rate of the aqueous film coating liquid, atomizing air pressure, drying time, amount of propylene glycol in the aqueous film coating liquid, temperature and the amount of aqueous film coating liquid applied. Analysis of the data shows that the amount of propylene glycol in the film was 81 to 96% less than the theoretical value when considering the amount of the propylene glycol in the aqueous film coating liquid. The loss of propylene glycol was independent of the variables studied. The loss of propylene glycol was also shown to occur in the Accela-Cota during the coating of tablets.