Effects of temperature on melt electrospinning with auxiliary heating: experiment and simulation study

2021 ◽  
pp. 004051752110582
Author(s):  
Cheng Ge ◽  
Yuansheng Zheng ◽  
Kai Liu ◽  
Binjie Xin
Keyword(s):  
High Speed ◽  
Heating Temperature ◽  
Good Deal ◽  
Electrospinning Process ◽  
Experimental Results ◽  
High Speed Photography ◽  
Auxiliary Heating ◽  
Jet Formation ◽  
Finite Element Software ◽  
Melt Electrospinning

In this study, the effect of the heating temperature of the spinneret on the melt electrospinning process under the condition of application of auxiliary heating was investigated, in a systematical and comprehensive way. The temperature distribution of the melt jet during the melt electrospinning process was simulated by finite element software in order to provide a good deal of insight into the experimental results. In addition, high-speed photography was adopted to capture images of jet formation and jet motion during the melt electrospinning process. The experimental results indicated that the cooling rate of the polypropylene jet decreases obviously under the condition of auxiliary heating; in addition, the higher spinneret temperature leads to greater drafting force, a drawing fiber drafting rate, and greater jet whipping motion, which is conducive to secondary drawing and refinement of the jet.

Experimental Investigation of the Characteristics of Dynamic Cutting Process

1977 ◽  
Vol 99 (2) ◽  
pp. 410-418 ◽  
Author(s):  
M. M. Nigm ◽  
M. M. Sadek
Keyword(s):  
Experimental Investigation ◽  
Theoretical Model ◽  
High Speed ◽  
Cutting Speed ◽  
Chip Thickness ◽  
Shear Plane ◽  
Rake Angle ◽  
Experimental Results ◽  
High Speed Photography ◽  
Cutting Coefficients

The dynamic response of the shear plane and the variations of the dynamic cutting coefficients are experimentally investigated at various values of feed, cutting speed, rake angle, clearance angle, frequency, and amplitude of chip thickness modulation. Wave generating and wave removing cutting tests, in which high-speed photography is used to investigate the geometry of chip formation, are carried out. The theoretical model of dynamic cutting developed in [1] is assessed with reference to these experimental results. A comparison between this model and previous models in relation to the experimental results is also presented.

Model development and validation of electrospun jet formation

2018 ◽  
Vol 89 (11) ◽  
pp. 2177-2186 ◽  
Author(s):  
Yuansheng Zheng ◽  
Binjie Xin ◽  
Masha Li
Keyword(s):  
High Speed ◽  
Volume Fraction ◽  
Model Development ◽  
Electrospinning Process ◽  
Taylor Cone ◽  
Jet Formation ◽  
Velocity Magnitude ◽  
Key Factor ◽  
Simulation Results ◽  
Development And Validation

The Taylor cone formed at the tip of the syringe used for delivering the solution plays an important role in jet formation. This study presents a novel multiphysics model to simulate the dynamic processes occurring within the cone jet from a flat spinneret and a single needle spinneret. The electric field, volume fraction and velocity magnitude of the polymer jet ejecting from two different kinds of spinnerets are calculated by the multiphysics simulation model. A high-speed camera is employed to capture the jet formed by the Taylor cone. The simulation results are validated by comparison with experimental results. It is found that the spinneret configuration could be the key factor in determining cone morphology in the electrospinning process.

scholarly journals Effects of Jet Path on Electrospun Polystyrene Fibers

Polymers ◽  
2018 ◽  
Vol 10 (8) ◽  
pp. 842 ◽  
Author(s):  
Yuansheng Zheng ◽  
Na Meng ◽  
Binjie Xin
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Surface Morphology ◽  
High Speed ◽  
Solution Concentration ◽  
Electrospinning Process ◽  
High Speed Photography ◽  
Fiber Mats ◽  
Jet Length ◽  
Scanning Electron

In this study we investigated the effects of jet path on the morphology and mat size of synthetic polystyrene (PS) fibers during the electrospinning process. In addition, the mechanism of the fiber mats, which were prepared by varying the solution concentration, was evaluated. The straight jet length, envelope cone and whipping frequency of each electrospun jet were studied using images captured by a high-speed photography camera. The results showed that higher solution concentrations led to longer straight jet lengths, smaller envelope cones and lower whipping frequencies. The diameter and surface morphology of the PS fibers were also characterized by scanning electron microscopy (SEM). It was found that fibers spun with higher solution concentrations exhibited larger diameters and diameter distributions because of their jet path features. Furthermore, the electrospun jets with higher concentrations increased elongation and produced smaller fiber mats and higher breaking forces as a result of their different jet paths, which was a consequence of varying the solution concentration.

Cavitation-Induced Interface Instability of Droplet Between Plates

2019 ◽  
Author(s):  
Hongchen Li ◽  
Jingzhu Wang ◽  
Yiwei Wang
Keyword(s):  
High Speed ◽  
Industrial Applications ◽  
High Speed Photography ◽  
Affecting Factors ◽  
Interface Instability ◽  
Jet Formation ◽  
Wave Impact ◽  
Two Phase ◽  
Droplet Shape ◽  
Bubble Pulsation

Abstract Interface instability of droplet and formation of the liquid jet caused by internal volume oscillation are directly related to liquid pumping and mixing of microfluidic devices. Complex morphology jet enables liquid shaping, which is advantageous for industrial applications and biomedical engineering. In this study, the interface instability of cylindrical droplet between plates is investigated. The problem is analyzed through numerical simulation and experimentation. In the experiment, a single-pulse laser is used to generate cavitation at the center of the cylindrical droplet between two polymethyl methacrylate plates, and the physical progress is captured by high-speed photography. A compressible two-phase solver in the open source code OpenFOAM is used to simulate the 3D progress of bubble pulsation and droplet jet in consideration of viscosity and surface tension. Numerical methods adopt large eddy simulation. Results show that the interface density gradient is not collinear with the pressure gradient due to the shock wave impact and the bubble pulsation, that is, the baroclinic effect is the main cause of the instability at the droplet interface. The mechanism of the radial jet formation in the first period of bubble pulsation is closely related to the interface instability. A pair of vortex rings is formed under the influence of instability, thereby causing a stacking phenomenon on the jet head and eventually being cut. Affecting factors of the instability of the droplet interface are discussed. A high instability intensity of the droplet interface can be caused by a large initial bubble energy and a small contact angle. The instability strength of the droplet interface and the mode of jet formation are very sensitive to the curvature of the initial droplet shape. Relevant results may provide a reference for further understanding of interface instability and related engineering applications.

Jet motion and fiber properties arising from a parallel electric field in melt-electrospinning

2020 ◽  
pp. 004051752096419
Author(s):  
Xueqin Li ◽  
Yuansheng Zheng ◽  
Xiaoqi Mu ◽  
Binjie Xin ◽  
Lantian Lin
Keyword(s):  
Electric Field ◽  
High Speed ◽  
Three Dimensional ◽  
Great Influence ◽  
Simulation Method ◽  
High Speed Photography ◽  
Outer Diameter ◽  
Electrospinning Technique ◽  
Fiber Properties ◽  
Melt Electrospinning

It is well known that the electric field has a great influence on the diameter and properties of fiber prepared via the melt-electrospinning technique. In this paper, two parallel metal discs were introduced to create a controllable electric field in the experiments. In addition, a three-dimensional electric field was calculated by the numerical simulation method and the jet motion was captured by taking advantage of high-speed photography technology. The influences of electric field distribution on the fiber jet, fiber diameter, fiber mat area and fiber crystallinity were studied in an in-depth and systematical manner. Both whipping amplitude and whipping frequency were also used to describe the characteristics of the jet. The above-mentioned results have proven that increasing the distance between the two parallel metal discs leads to the decrease of electric field intensity and the increase of electric field action time on the fiber, which together determine the diameter and crystallinity of the fiber. With the increase of the outer diameter of the upper disc, the distribution of the electric field becomes more uniform, making it capable of steadily controlling the behavior of the jet, and thus effectively reducing the diameter of the fiber and improving the crystallinity of the fiber.

Effect of Loading Rate on Failure in Bulk Metallic Glasses

2002 ◽  
Vol 754 ◽  
Author(s):  
T. Jiao ◽  
C. Fan ◽  
L.J. Kecskes ◽  
T.C. Hufnagel ◽  
K.T. Ramesh
Keyword(s):  
Metallic Glasses ◽  
High Speed ◽  
Dynamic Compression ◽  
Failure Process ◽  
Compressive Loading ◽  
Shear Bands ◽  
Bulk Metallic Glasses ◽  
Experimental Results ◽  
Dynamic Strain ◽  
High Speed Photography

ABSTRACTWe have investigated failure in bulk metallic glass-forming alloys under dynamic compression. We implemented a recovery technique for the compression Kolsky bar to obtain dynamically deformed, intact specimens at various stages of deformation; this allows us to characterize the development of failure. We have also used high-speed photography to examine the failure process during the recovery experiments. The experimental results indicate that the failure under dynamic loading is somewhat different from that under quasi-static loading. Specimens subjected to quasistatic deformation developed multiple shear bands and substantial plastic deformations, while specimens subjected to dynamic (—strain rate ∼103 s-1) compressive loading fail by fracture along one dominant shear band. The mechanisms of dynamic failure in bulk metallic glasses are discussed on the basis of these experimental results.

scholarly journals DEM-CFD Simulation and Experiments on the Flow Characteristics of Particles in Vortex Pumps

Water ◽  
2020 ◽  
Vol 12 (9) ◽  
pp. 2444
Author(s):  
Xiongfa Gao ◽  
Weidong Shi ◽  
Ya Shi ◽  
Hao Chang ◽  
Ting Zhao
Keyword(s):  
Numerical Simulation ◽  
High Speed ◽  
Cfd Simulation ◽  
Flow Characteristics ◽  
Solid Particles ◽  
Experimental Results ◽  
High Speed Photography ◽  
Inlet Section ◽  
Impeller Blade ◽  
Vortex Pump

Due to their outstanding anti-clogging ability, vortex pumps have been gradually promoted and applied in recent years. However, when transporting sewage containing solids, they will still encounter problems such as partial clogging, overwork wear, etc., therefore, it is particularly important to master the flow characteristics of solid particles in the vortex pump. In this paper, the Discrete Element Model-Computational Fluid Dynamics (DEM-CFD) coupled calculation method is introduced into the numerical simulation of vortex pumps and particles with diameters of 1, 2 and 3 mm and concentrations of 1% and 5%, were subjected to numerical simulation and study of the flow characteristics of the particles, then rapeseed was used to represent solid particles in tests. It was obvious that the CFD results were in good agreement with the experimental results, whereby the high speed photography experimental results of the pump inlet section show that the experimental results are consistent with the numerical simulation results. The results show that there are three typical movement tracks of solid particles in the vortex pump: in Track A particles flow through the impeller and enter the volute by the through flow, in Track B particles go directly into the volute through the lateral cavity under the influence of circulation flow and in Track C the particles enter the impeller from the front cover end area of the impeller blade inlet and then into the volute through the back half area of blade. It can be found that the particles are mainly distributed at the back of the volute.

scholarly journals Bubble Melt Electrospinning for Production of Polymer Microfibers

Polymers ◽  
2018 ◽  
Vol 10 (11) ◽  
pp. 1246 ◽  
Author(s):  
Ye-Ming Li ◽  
Xiao-Xiong Wang ◽  
Shu-Xin Yu ◽  
Ying-Tao Zhao ◽  
Xu Yan ◽  
...  
Keyword(s):  
High Speed ◽  
Fiber Diameter ◽  
Heating Temperature ◽  
Polymer Melt ◽  
Taylor Cone ◽  
Ultrafine Fibers ◽  
Melt Electrospinning ◽  
Spinning Process ◽  
Metal Needle ◽  
Polymer Microfibers

In this paper, we report an interesting bubble melt electrospinning (e-spinning) to produce polymer microfibers. Usually, melt e-spinning for fabricating ultrafine fibers needs “Taylor cone”, which is formed on the tip of the spinneret. The spinneret is also the bottleneck for mass production in melt e-spinning. In this work, a metal needle-free method was tried in the melt e-spinning process. The “Taylor cone” was formed on the surface of the broken polymer melt bubble, which was produced by an airflow. With the applied voltage ranging from 18 to 25 kV, the heating temperature was about 210–250 °C, and polyurethane (TPU) and polylactic acid (PLA) microfibers were successfully fabricated by this new melt e-spinning technique. During the melt e-spinning process, polymer melt jets ejected from the burst bubbles could be observed with a high-speed camera. Then, polymer microfibers could be obtained on the grounded collector. The fiber diameter ranged from 45 down to 5 μm. The results indicate that bubble melt e-spinning may be a promising method for needleless production in melt e-spinning.

Dynamics of laser-induced cavitation bubbles near an elastic boundary

2001 ◽  
Vol 433 ◽  
pp. 251-281 ◽  
Author(s):  
EMIL-ALEXANDRU BRUJAN ◽  
KESTER NAHEN ◽  
PETER SCHMIDT ◽  
ALFRED VOGEL
Keyword(s):  
High Speed ◽  
Bubble Dynamics ◽  
Complex Dynamics ◽  
Water Concentration ◽  
Water Layer ◽  
Liquid Jets ◽  
High Speed Photography ◽  
Jet Formation ◽  
Elastic Boundary ◽  
Bubble Splitting

The interaction of a laser-induced cavitation bubble with an elastic boundary and its dependence on the distance between bubble and boundary are investigated experimentally. The elastic boundary consists of a transparent polyacrylamide (PAA) gel with 80% water concentration with elastic modulus E = 0.25 MPa. At this E-value, the deformation and rebound of the boundary is very pronounced providing particularly interesting features of bubble dynamics. It is shown by means of high-speed photography with up to 5 million frames s−1 that bubble splitting, formation of liquid jets away from and towards the boundary, and jet-like ejection of the boundary material into the liquid are the main features of this interaction. The maximum liquid jet velocity measured was 960 m s−1. Such high-velocity jets penetrate the elastic boundary even through a water layer of 0.35 mm thickness. The jetting behaviour arises from the interaction between the counteracting forces induced by the rebound of the elastic boundary and the Bjerknes attraction force towards the boundary. General principles of the formation of annular and axial jets are discussed which allow the interpretation of the complex dynamics. The concept of the Kelvin impulse is examined with regard to bubble migration and jet formation. The results are discussed with respect to cavitation erosion, collateral damage in laser surgery, and cavitation-mediated enhancement of pulsed laser ablation of tissue.

A Study of White Smoke Generation and Its Numerical Simulation

1993 ◽  
Vol 207 (2) ◽  
pp. 101-106 ◽  
Author(s):  
T Shiozaki ◽  
T Otani ◽  
I Joko
Keyword(s):  
Numerical Simulation ◽  
High Speed ◽  
Experimental Results ◽  
Fuel Spray ◽  
High Speed Photography ◽  
Visualization Technique ◽  
Lean Mixture ◽  
Smoke Generation

A mechanism of white smoke generation is clarified by a visualization technique using high-speed photography. The adhered fuel spray on the wall of the cavity, the fuel in the lean mixture region, the spilled fuel from the combustion cavity and the fuel from the sac volume of the nozzle tip are converted to the white smoke late in the expansion stroke. Numerical simulation is also conducted and its results coincide well with experimental results.

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