scholarly journals Measurement and Comparison of Melt-Blowing Airflow Fields: Nozzle Modifications to Reduce Turbulence and Fibre Whipping

Polymers ◽  
2021 ◽  
Vol 13 (5) ◽  
pp. 719
Author(s):  
Ying Yang ◽  
Yongchun Zeng
Keyword(s):  
Turbulence Intensity ◽  
Temperature Fluctuation ◽  
High Speed ◽  
Aerodynamic Force ◽  
High Speed Photography ◽  
Melt Blowing ◽  
Fluctuation Intensity ◽  
Slot Die ◽  
Turbulent Airflow ◽  
Airflow Field

In the melt-blowing process, micro/nanofibrous nonwovens are attenuated and formed through aerodynamic force in a turbulent airflow field. In this work, two types of airflow-directors were added under a common melt-blowing slot-die nozzle to obtain modified airflow fields. The effect of airflow-directors on time-averaged characteristics, turbulence intensity, and temperature fluctuation intensity are achieved through the simultaneous measurement of fluctuating velocity and fluctuating temperature using a two-wire probe hot-wire anemometer. Moreover, the influence of airflow-directors on fibre oscillations are also investigated through high-speed photography. The distribution of turbulence intensity and temperature fluctuation intensity reveals the characteristics of fluctuating airflow fields formed by different melt-blowing slot-die nozzles. Through the analyses of airflow characteristics and fibre oscillations, we can find that the arrangement of airflow-directors has a great impact on both turbulence distribution and fibre oscillation.

scholarly journals Lateral Diffusion of a Free Air Jet in Slot-Die Melt Blowing for Microfiber Whipping

Polymers ◽  
2019 ◽  
Vol 11 (5) ◽  
pp. 788 ◽  
Author(s):  
Sheng Xie ◽  
Wanli Han ◽  
Xufan Xu ◽  
Guojun Jiang ◽  
Baoqing Shentu
Keyword(s):  
High Speed ◽  
Lateral Diffusion ◽  
Polymer Melt ◽  
Nonwoven Material ◽  
Fiber Formation ◽  
High Speed Photography ◽  
Melt Blowing ◽  
Lateral Velocity ◽  
Air Jet ◽  
Slot Die

In melt blowing, microfibrous nonwoven material is manufactured by using high-speed air to attenuate polymer melt. The melt-blown air jet determines the process of polymer attenuation and fiber formation. In this work, the importance of lateral velocity on the fiber was first theoretical verified. The lateral diffused characteristic of the air flow field in slot-die melt blowing was researched by measuring the velocity direction using a dual-wire probe hot-wire anemometer. Meanwhile, the fiber path was captured by high-speed photography. Results showed that there existed a critical boundary of the lateral diffusion, however, air jets in the x–z plane are a completely diffused field. This work indicates that the lateral velocity in the y–z plane is one of the crucial factors for initiating fiber whipping and fiber distribution.

Simulation of jet velocity in the melt-blowing process using the coupled air–polymer model

2018 ◽  
Vol 89 (16) ◽  
pp. 3221-3233 ◽  
Author(s):  
Xibo Hao ◽  
Hui Huang ◽  
Yongchun Zeng
Keyword(s):  
High Speed ◽  
Flow Model ◽  
Processing Parameters ◽  
High Speed Photography ◽  
Critical Factors ◽  
Polymer Model ◽  
Melt Blowing ◽  
Two Phase ◽  
Jet Velocity ◽  
Jet Velocities

The polymer jet velocity is one of the most basic and critical factors in the melt-blowing process and has always been difficult to measure online. Much effort has been made on the numerical prediction of the jet velocity. However, little work has involved the complex interaction between the air flow and the polymer. Here, the Level-Set method is used to develop the coupled air–polymer two-phase flow model, and to simulate the polymer jet motion in the melt-blowing process considering the coupled effect of the air and polymer. Meanwhile, high-speed photography is adopted in the experiments to verify the simulation results. The x- and y-components of the jet velocities and the whipping amplitude of the jet motion are discussed. The rapid increase of jet velocity and the decrease of jet diameter show that most attenuation of the polymer jet occurred within a distance close to the die (10 mm). Based on the model, the effects of the processing parameters on the jet velocity are examined numerically.

Effect of slot end faces on the three-dimensional airflow field from the melt-blowing die

2020 ◽  
Vol 40 (7) ◽  
pp. 607-613
Author(s):  
Yudong Wang ◽  
Jianping Zhou
Keyword(s):  
Numerical Calculation ◽  
Flow Field ◽  
Field Distribution ◽  
Three Dimensional ◽  
Central Area ◽  
Computational Domain ◽  
Melt Blowing ◽  
Slot Die ◽  
Calculation Results ◽  
Airflow Field

AbstractIn order to investigate the effect of the slot ends of the melt-blowing die on the three-dimensional airflow field distribution and the fiber draft, the numerical calculation was carried out. The computational domain of the slot die was established with Gambit, and the flow field was calculated using FLUENT. Compared with the experimental data collected by a hot-wire anemometer, the numerical calculation results are credible. The results show that the slot end face has a certain influence on the three-dimensional flow field distribution under the melt-blowing die. The air velocity and temperature in the center region are quite different from those near the slot-end face. As the distance from the center of the flow field increases, the velocity and temperature on the spinning line begin to decrease. The velocity and temperature distributions of the spinning lines in the central area and nearby areas are almost the same; the temperature and velocity values on the spinning lines near the slot end are the lowest. The distribution characteristics of the three-dimensional airflow field could affect the uniformity of the fiber diameter and the meltblowing products.

Numerical and experimental study on the joint forming mechanism in the pneumatic splicing process

2019 ◽  
Vol 89 (21-22) ◽  
pp. 4512-4525
Author(s):  
Yingjie Zhou ◽  
Zhenyu Wu ◽  
Yisheng Liu ◽  
Zhong Xiang ◽  
Xudong Hu
Keyword(s):  
High Speed ◽  
Aerodynamic Force ◽  
Contact Friction ◽  
Dynamics Model ◽  
Spiral Flow ◽  
Friction Behavior ◽  
Forming Mechanism ◽  
Airflow Field ◽  
Fixed End ◽  
Rotating Channel

This study presents an investigation on the joint forming mechanism of pneumatic splicing by numerical and experimental methods. A one-way coupling numerical model concerning interaction between fluid and filaments was established to simulate the complex motion of a flexible body in a spiral flow field. The airflow field in the splicing chamber, which contributes to longitudinal and normal aerodynamic force along a filament regarded as a digital chain composed of a series of interconnected rods, was obtained by a two-equation turbulent computational fluid dynamics model. Contact-friction behavior within filaments was also taken into consideration. An iterative algorithm was adopted to update the displacement of filaments and the corresponding aerodynamic force. A high-speed visualization test bench was built to record the sequence motion of filaments in the splicing process. The splicing mechanism within flexible filaments was identified by comparison between the experimental data and numerical results. The filament portion located in the homolateral rotating channel with respect to orifice is blown to bent by the jet airflow. It contributes to a frontal area in the axial airflow direction, causing the filament to be retracted toward its fixed end. Meanwhile, the portion in the contralateral rotating channel tries to wrap around the opposite filaments due to the spiral airflow. The interaction between filaments generates the contact force and related friction force, which commonly resists the retracting force exerted on the homolateral filament portion. The competition between the two forces determines whether the joint can be formed. Furthermore, the influence of the overlapping length on splicing behavior was discussed.

A Geometry Method for Calculating the Fiber Diameter Reduction in Melt Blowing

2014 ◽  
Vol 893 ◽  
pp. 87-90 ◽  
Author(s):  
Sheng Xie ◽  
Yong Chun Zeng
Keyword(s):  
High Speed ◽  
Fiber Diameter ◽  
Mechanical Analysis ◽  
Diameter Distribution ◽  
High Speed Photography ◽  
Melt Blowing ◽  
Ultrafine Fibers ◽  
Online Measurements ◽  
Fiber Diameter Distribution ◽  
Diameter Reduction

Melt blowing is one of the important methods for producing ultrafine fibers. The production of melt blowing is the nonwoven. Fiber diameter has crucial effect on the property of the nonwovens. In the melt-blowing process, many achievements have been published on the fiber diameter distribution along the spinning line. Note that all the results were obtained by methods of mechanical analysis, online measurements through high-speed photography and offline measurements from the production of nonwoven. In this study, a new method for calculating the fiber diameter distribution along the spinning line near the die face was revealed. This method was based on the geometry of the fiber path in the melt-blowing process. The fiber diameter reduction was calculated by this method and then compared with the experimental results obtained by other researchers. The results show that the proposed method is feasible.

scholarly journals Modeling the airflow field of vortex spinning

2021 ◽  
pp. 004051752110569
Author(s):  
Shanshan Shang ◽  
Zikai Yu ◽  
Guangwu Sun ◽  
Chongwen Yu ◽  
R Hugh Gong ◽  
...  
Keyword(s):  
High Speed ◽  
Three Dimensional ◽  
Wall Function ◽  
Great Insight ◽  
Spinning Process ◽  
Turbulent Airflow ◽  
Region Model ◽  
Airflow Field ◽  
Control Volumes ◽  
Insight Into

Vortex spinning technology adopts a high-speed swirling airflow to rotate the fibers with open-ends to form yarn with real twists. The airflow behavior within the nozzle has a great effect on the yarn-formation process. In this study, a three-dimensional calculation nozzle model and corresponding three-dimensional airflow region model were established to enable the numerical calculation; airflow behavior—pressure, velocity, and the turbulent airflow field, and the streamline of airflow—was investigated in the presence of fiber bundles within the vortex spinning nozzle. Hybrid hexahedral/tetrahedral control volumes were utilized to mesh the grids in the calculation region. To consider airflow diffusion and convection in the nozzle, the Realizable k- ε turbulence model with wall function was adopted to conduct the calculation. Dynamic and static pressure values were obtained by numerical analysis to predict the action of the inner surface of nozzle and the wall resistance on the high-speed swirling airflow. The numerical simulation of dynamic airflow behavior can generate great insight into the details of airflow behavior and its distribution characteristics, and is helpful for understanding the spinning mechanism and promoting optimization of the spinning process.

scholarly journals A Modified Quasisteady Aerodynamic Model for a Sub-100 mg Insect-Inspired Flapping-Wing Robot

2020 ◽  
Vol 2020 ◽  
pp. 1-12
Author(s):  
Chenyang Wang ◽  
Weiping Zhang ◽  
Junqi Hu ◽  
Jiaxin Zhao ◽  
Yang Zou
Keyword(s):  
High Speed ◽  
Aerodynamic Force ◽  
Flapping Wing ◽  
High Speed Photography ◽  
Wing Kinematics ◽  
Blade Element Theory ◽  
Passive Rotation ◽  
Aerodynamic Model ◽  
Proposed Model ◽  
Element Theory

This study proposes a modified quasisteady aerodynamic model for the sub-100-milligram insect-inspired flapping-wing robot presented by the authors in a previous paper. The model, which is based on blade-element theory, considers the aerodynamic mechanisms of circulation, dissipation, and added-mass, as well as the inertial effect. The aerodynamic force and moment acting on the wing are calculated based on the two-degree-of-freedom (2-DOF) wing kinematics of flapping and rotating. In order to validate the model, we used a binocular high-speed photography system and a customized lift measurement system to perform simultaneous measurements of the wing kinematics and the lift of the robot under different input voltages. The results of these measurements were all in close agreement with the estimates generated by the proposed model. In addition, based on the model, this study analyzes the 2-DOF flapping-wing dynamics of the robot and provides an estimate of the passive rotation—the main factor in generating lift—from the measured flapping kinematics. The analysis also reveals that the calculated rotating kinematics of the wing under different input voltages accord well with the measured rotating kinematics. We expect that the model presented here will be useful in developing a control strategy for our sub-100 mg insect-inspired flapping-wing robot.

The Effect of Air Pressure on the Evolution of Fiber Path in Melt-Blowing Process

2014 ◽  
Vol 852 ◽  
pp. 496-500
Author(s):  
Sheng Xie ◽  
Yong Chun Zeng
Keyword(s):  
High Speed ◽  
Air Pressure ◽  
High Speed Camera ◽  
Pressure Condition ◽  
Melt Blowing ◽  
Attenuation Effect ◽  
Ultrafine Fibers ◽  
Important Method ◽  
Slot Die ◽  
Fiber Path

Melt blowing is an important method for producing ultrafine fibers. In melt blowing process, compared to the studies on the fiber path at a certain air pressure condition, much less has been done on searching the evolution of the fiber paths at different air pressures. In this study, a high-speed camera was used to capture the fiber paths below a slot die and a swirl die in the melt-blowing process. The evolution of the fiber paths was captured. This paper first shows the evolution of the fiber paths at different air pressures, which is useful to further understand the attenuation effect on the fiber in the melt-blowing process.

scholarly journals Particle Image Velocimetry (PIV) Investigation of the Turbulent Airflow in Slot-Die Melt Blowing

Polymers ◽  
2020 ◽  
Vol 12 (2) ◽  
pp. 279 ◽  
Author(s):  
Sheng Xie ◽  
Guojun Jiang ◽  
Baolin Ye ◽  
Baoqing Shentu
Keyword(s):  
Particle Image Velocimetry ◽  
Particle Image ◽  
Air Velocity ◽  
Melt Blowing ◽  
Forming Mechanism ◽  
Piv Technique ◽  
Image Velocimetry ◽  
Slot Die ◽  
Turbulent Airflow

In order to explore the forming mechanism of the fiber whipping motion in slot-die melt blowing, the turbulent airflow in slot-die melt blowing was measured online with the approach of the Particle Image Velocimetry (PIV) technique. The PIV results visualized the structure of the turbulent airflow and provided the distributions of air velocity components (vx, vy, and vz). Moreover, the PIV results also demonstrated the evolutive process of turbulent airflow at successive time instants. By comparing the characteristics of the turbulent airflow with the fiber whipping path, the PIV results provide a preliminary explanation for the specific fiber whipping motion in slot-die melt blowing.

scholarly journals Crosswind Effects on Interaction Performance of High-speed Railway Pantograph-catenary System: A Case Study in Chengdu-Chongqing Passenger Special Railway

2021 ◽  
Author(s):  
Yang Song ◽  
Fuchuan Duan ◽  
Shibin Gao ◽  
Fanping Wu ◽  
Zhigang Liu ◽  
...  
Keyword(s):  
Turbulence Intensity ◽  
High Speed ◽  
Aerodynamic Force ◽  
Measurement Data ◽  
Lumped Mass ◽  
Mass Model ◽  
Safety Issues ◽  
Drag Forces ◽  
Operational Safety ◽  
Catenary System

Abstract As a common disturbance to the railway pantograph-catenary system, the crosswind may deteriorate the current collection quality and threat operational safety. The main topic of this paper is to study the effect of crosswind on the interaction performance of pantograph-catenary considering the aerodynamic forces acting on both the pantograph and catenary. The pantograph-catenary system of the Chengdu-Chongqing passenger special railway is adopted as the analysis object. The absolute nodal coordinate formulation (ANCF) is employed to build the catenary model, of which the numerical accuracy is validated via the comparison with the field measurement data collected from an inspection vehicle operating at 378 km/h. A special spatial grid is defined for the pantograph-catenary system to generate the stochastic wind field based on the empirical spectrum. According to the quasi-steady theory, the wind load acting on the catenary is derived. Computational fluid dynamics (CFD) is employed to calculate the lift and drag forces acting on each component of the pantograph, which are used to derive the equivalent aerodynamic force that can be applied in the lumped-mass model. The simulation results indicate that the pantograph-catenary system of Chengdu-Chongqing passenger special railway has an acceptable performance with a crosswind speed of 20 m/s. But when the crosswind increases up to 30 m/s, some contact force statistics exceed the safety threshold with a turbulence intensity of more than 17%. Through the analysis of the operational safety, it is found that the contact wire always works within the safety range of the pantograph head with a crosswind speed of 30 m/s. But some safety issues can be seen from the maximum uplift of the pantograph head with a turbulence intensity of more than 21%.

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