Design and experiment of a needle-type piezostack-driven jetting dispenser based on lumped parameter method

Micro liquid dispensing technology is widely used in the field of electronic packaging. This study presents a lumped parameter model of a needle-type piezostack-driven jetting dispenser, which can produce small high viscosity adhesive droplets with a high driving frequency. After describing the structural components and operating principles of the dispenser, a lumped parameter model for the system is derived by integrating the sub-models of the structural and fluid parts. According to the lumped parameter method, the fluid channels of the dispenser have been divided into several lumps to obtain a more accurate performance. Based on the proposed model, the jetting dispenser is designed and manufactured, and its performance is then evaluated through both computer simulations and experiments. Further experimental studies about its working properties based on the proposed dispenser are carried out. The results are used to guide the design and control works about the proposed dispenser.     

Simulation and experiment study on adhesive ejection behavior in jetting dispenser

In this paper, fundamental equations for jetting dispenser are presented to express the influence of adhesive pressure, nozzle diameter, and needle movement law, and the equations are then verified by flow behavior simulation. Subsequently, a novel jetting dispenser system is built to finish experiments about the mentioned influence parameters, and simulation results verify the regularities from experiment are correct. Flow velocity in the central nozzle will be faster and radius of the droplet will be bigger if the pressure in the chamber became higher, flow velocity in the central nozzle will be constant and the radius of the droplet will be bigger if the dead time became longer, and bigger nozzle diameter can lead to faster flow velocity in the central nozzle and bigger droplet. Besides, these mentioned works prove that our designed jetting dispenser is practical and useful for adhesive jetting.     

Dispensing of rheologically complex fluids: The map of misery

Rheological effects may complicate the dispensing of complex fluids, when compared to their Newtonian counterparts. In this work, fluids with tailored rheological properties have been studied using high‐speed video‐microscopy. The level of viscosity, the degree of shear thinning, and the elasticity have been varied independently. At low‐flow rates, droplets are formed that pinch off. The drop volumes, breakup mechanisms, and times have been identified. At higher‐flow rates, a continuous jet is observed, with the transition depending on the rheology of the dispensed fluid. The relevant nondimensional groups are the Ohnesorge, Deborah, and elasto‐capillary number, for when viscosity, inertia, or elastic forces dominate flow. In each of these cases, the transition between dripping and jetting dispensing occurs, controlled by a critical Weber, capillary, and Weissenberg number, respectively. This set of six nondimensional groups can be used to construct an operating space and map out areas of potential problems. © 2011 American Institute of Chemical Engineers AIChE J, 58: 3242–3255, 2012     

A temperature-responsive dual network hydrogel for reversible smart actuator

Nowadays, soft actuators have received extensive attention in many application fields, among which hydrogels have become an important choice for constructing soft actuators due to their unique properties. However, the actuating behaviors of hydrogel-based actuators are usually monotonous due to their unchangeable shapes and structures. Herein, we report a temperature-responsive hydrogel actuator with a bilayer structure. Based on the dual network structure (polyvinyl alcohol/poly acrylamide and polyvinyl alcohol/poly (N-isopropylacrylamide), the actuators can realize the reinforcement compared with the single network. Because of the intrinsic lower critical solution temperature of poly (N-isopropylacrylamide, both sides of actuators have different swelling rates, enabling them to achieve the thermal-responsive actuation and shape programming. Therefore, this work is promising to provide a new strategy for designing temperature switches and thermally driven soft robots.     

小直径钻头层次优选AHP模型的确立及应用

钻井中,钻头费用在1口井的总投资里所占的比例一般不大,但钻头的使用效果会直接影响整个钻井。由于小直径钻头的特殊性,轴强度低,落井后不易打捞,以及转速、钻压、井下工具等因素的限制,小直径钻头的优选较常规尺寸更重要,在进行小直径钻头评价和优选时,每种类型的小直径钻头都包含有各类技术经济指标,很多指标既相互依赖,又相互矛盾,因而给决策、评价带来很大困难。另外,决策人员有时很容易受某一具体指标的影响,常常会单凭一项经济或技术指标而肯定或否定某一类型的钻头。为此,本文对中原油田小井眼(458″)钻头尝试运用综合评价法中的层次分析(AHP,A nalyticH ierarchy Process)理论进行评价与优选。     

注塑件喷射纹的形成机理及其解决措施

阐述了注塑件喷射纹的形成根本机理,分析了喷射纹对制件性能的影响,并结合大量实例,从模具设计、成型工艺、材料、产品设计等方面提出避免或减轻喷射纹的措施。     

Detailed investigation of effects of operating parameters of ultrafiltration using laboratory-scale ultrafiltration unit

Cross flow ultrafiltration is a pressure driven membrane process in which the fluid to be filtered flows parallel to the membrane surface. The formation of filter cake can be reduced by scouring force of the flow, thus better permeate rate is obtained.

Laboratory-scale ultrafiltration experiments with Polyvinyl Alcohol (PVA) solution of known molecular weight was carried out to study the membrane filter performances with respect to operating parameters. These operating parameters included, membrane molecular weight cut off size, molecular weight of PVA, influent concentration, cross flow velocity and applied pressure. It was discovered that clogging in the membrane occurs quite slowly during first 30 minutes, and quasi-steady state was noticed normally after 50 minutes of filtration time. In this study, steady state flux data were used to develop semi-empirical and empirical correlations which are useful in the optimum design of ultrafiltration.     

高压水清理施工应该注意的一些事情

高压水清理技术因其是在超高压条件下施工,由此带来的施工安全问题必须引起足够的重视。本文介绍了高压水清理设备的基本组成,高压水清理对施工人员可能造成的危害,可以采用的合适的安全防护器具,正常的工作压力等,以使施工人员熟悉高压水设备的正确使用方法。     

Improved chemical resistance of ink‐jet printed micropatterns on glass by using dual‐functional compositions

UV curable and UV/moisture dual‐functional oligomers were synthesized by grafting trimethoxysilane and methacrylate segments on the polyimide oligomer chains. These oligomers and a dual‐functional monomer were used as ink compositions to enhance the chemical resistance of ink‐jet printed LCD color filter micropatterns, without sacrificing jetting performance. The molecular structure and molecular weight of the oligomers were altered to adjust the solubility of oligomer in monomers, together with jetting trajectory, drop size uniformity, and deposition accuracy of the ink‐jet inks. The chemical resistance, optical property, and mechanical property of the printed patterns depend on the oligomer structure, the arrangement of trimethoxysilane groups, and the molecular chain length. Straight lines and uniform dot arrays with excellent chemical resistance can be achieved. Dot patterns made of polymer‐silica hybrid materials and pigments remain unchanged after being immersed in γ‐butyrolactone for 200 min. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 2049–2055, 2013     

蒸汽喷射式抽空器变工况性能及分析

炼油厂减压蒸馏装置中的减压塔一般采用蒸汽喷射式抽空器来实现塔内的真空。在实际生产运行中 ,工作蒸汽的参数是不稳定的 ,而且处理量也是变化的。针对这种状况 ,推导了绝热指数的计算公式并建立了蒸汽抽空器的计算模型 ,用蒸汽作为引射气体进行了计算 ,并对变工况条件下蒸汽抽空器的性能及进行了分析。     

相容性对合金分离膜结构和性能的影响

介绍了相容性对合金膜的结构和性能的意义。液相共混高分子合金膜的结构与其共混体系的相容性密切相关 ,影响合金体系相容性的因素包括共混体系的性质、组成、分子结构、分子质量、结晶度、增塑作用、溶剂和操作温度等 ,因此可以通过以上途径来调控合金体系的相容性 ,进而得到理想的膜性能     

德士古气化炉气化过程剖析（Ⅲ）—停留时间分布测试

介绍７种不同规格容器、６种工况下的停留时间分布测试结果，定性地分析了影响停留时间分布的因素，诸如射流速度、高径比、筒体直径与喷嘴直径比、出口阻力等。研究表明，德士古气化炉基本上趋于全混流，约有５０％左右的物料在平均停留时间之前离开炉膛，存在短路，停留时间不足一秒，已见物料逸出炉外。     

CSP电站汽轮机选型分析

与传统火电用汽轮机不同,光热发电用汽轮机具有机组容量相对较小、受环境影响因素多、每天频繁启停、运行负荷低等特点。尽管光热电站中汽轮机投资的占比较小,但汽轮机效率对整个电站经济性至关重要。本文阐述了光热电站主机特点和供应商情况,分析了汽轮机进汽、排汽参数的选取要点,以及工况设定原则和注意事项,为开展光热电站主机选型提供指导和建议。     

Synthesis of UV and thermal dual curing oligomer for solder resist ink using ink-jet printing

A novel solder resist ink for inkjet printing containing the ultraviolet (UV) and thermal dual curing oligomer is introduced in this work. Three kinds of acrylic monomers for the synthesis of the oligomer are successful prepared and their structures are determined by Fourier transfer infrared. Both UV curing process and thermostability are monitored under UV differential scanning calorimetry and thermogravimetric analysis. For the photoreaction process, the oligomer using Lauryl methacrylate as the material of copolymerization possesses the highest reactivity and conversion of carbon–carbon double bond. Besides, this kind of oligomer also owns excellent thermostability, just losing 5.9% of its weight at 288 °C. The solder resist inks containing the oligomers and jetting by the inkjet printer are tested with the adhesion, soldering resistance, and other performances, presenting the outstanding heat resistance and wide application prospects. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47428.     

Experimental and numerical study of fluid dynamic parameters in a jetting fluidized bed of a binary mixture

The solid circulation pattern, the voidage profile, and the jet penetration height have been investigated experimentally and computationally in a cold-flow model of jetting fluidized beds (JFBs) of a binary mixture in this paper. This rectangular two-dimensional bed is 0.30 m wide and 2.05 m high with a central jet and a conical distributor, which roughly stands for the ash-agglomerating fluidized-bed coal gasifier. A video camera and coloured particle tracer method were employed to explore the fluid dynamics in the bed. In terms of the average physical properties of binary mixtures, a hydrodynamic model describing the gas-solid flow characteristics in a jetting bed is resolved by using a modified Semi-Implicit Method for Pressure-Linked Equation (SIMPLE) algorithm. This paper focuses on three features of the fluid dynamics—solid circulation pattern, voidage profile, and jet penetration height. The solid circulation pattern is composed of three regions: the jetting region, the bubble street, and the annular region. Above the central nozzle the time-averaged isoporosity contours are almost elliptic, while near the walls of the bed, the voidage in high solid concentration region is approximately equal to that at the minimum fluidization state. The jet penetration height increases with increasing jet gas velocity and with decreasing average particle diameter. The increase in weight percentage of the lighter component in the binary system reveals that reduction of average density causes the enlargement of jet penetration height. The simulated results show good agreement with the experimental data.     

Performance analysis of an adsorption refrigerator using activated carbon in a compound adsorbent

To improve the performance of the adsorption refrigeration of CaCl₂-ammonia adsorption system, activated carbon has been distributed uniformly in the mass of CaCl₂, thereby helping to enhance mass transfer and uplift the cooling power density. A multifunctional heat pipe adsorption refrigerator, in which activated carbon-CaCl₂ is used as compound adsorbent and ammonia as refrigerant, is designed. Water and acetone are used as working liquids for the heat pipe. This paper presents a study on the adsorption refrigeration performances of this adsorption refrigerator under two different working conditions, ice-maker for fishing boat driven by the waste heat from exhaust gases, and solar ice-maker driven by solar water heating. The obtained average SCP (specific cooling power) and the COP (coefficient of performance) of the refrigerator were measured to be 770.4 W/kg and 0.39 at about −20 °C of evaporating temperature for the former working condition, and they were 161.2 W/kg and 0.12 at about −15 °C of evaporating temperature for the later working condition.     

陶瓷过滤管用扩压管式引射器脉冲喷吹系统的研究

通过对陶瓷过滤管用扩压管式引射器脉冲喷吹系统的动态特性研究，分析了引射器结构参数和操作参数对其反吹性能的影响，为研究扩压管式引射器的机理及其优化设计提供了依据     

单螺杆FDM线材挤出机机筒结构分析与优化设计

对机筒的加热器位置、机筒长度和机筒内径等影响单螺杆FDM线材挤出机挤出成型的机筒结构因素进行了分析,以压力梯度、出口平均温度和流场平均温度为试验指标,基于ANSYS Workbench软件进行正交试验和极差分析,得到最优因素组合。并在试压工况、正常工况、极限工况和极限冷态工况等4种工况下,对采用最优因素组合设计的机筒进行了热力耦合试验验证。试验结果表明:当机筒的加热器位置43 mm、机筒长度270 mm、机筒内径15 mm时,单螺杆FDM线材挤出机出丝顺利,效率较高且安全可靠。     

Unconfined fluid electrospun into high quality nanofibers from a plate edge

We demonstrate an easily-implemented, edge-plate geometry for electrospinning and produce high quality nanofibers from unconfined polymer fluids. We show that for electrospinning in general, the electric field gradient, not just the electric field amplitude, is a critical parameter for successful self-initiated jetting. Considering a single spinning site, the edge-plate configuration resulted in the same or a higher fabrication rate as traditional needle electrospinning, while producing nanofibers similar in quality (diameter, diameter distribution, and collected mat porosity); moreover, this novel configuration operates without the possibility of clogging and has high potential for scale-up. We analyze the fundamental physical processes which underlie edge-plate electrospinning, including electric field, working distance, and feed rate dependence and the resultant changes to the linear and whipping regions, and thus to the fiber diameter. We conclude that the edge-plate configuration functions in a remarkably similar manner to traditional needle electrospinning.