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Dimitrios V Papavassiliou - One of the best experts on this subject based on the ideXlab platform.

  • modifying air fields to improve Melt Blowing
    Industrial & Engineering Chemistry Research, 2012
    Co-Authors: E R Shambaugh, Dimitrios V Papavassiliou, Robe L Shambaugh
    Abstract:

    An advanced model for Melt Blowing was used to predict the effects of modified air fields on fiber formation. The model, which was developed previously, involves the simultaneous solution of the momentum, energy, and continuity equations. Crystallization effects were included. The model equations were solved numerically. Simulations were done for two classes of modified air fields. The first class of modified air field has a plateau of constant velocity and temperature. For wide plateaus placed near the die face, the effect of the plateau is substantial. Fiber diameters are reduced (by up to two times) versus diameters for when there is no plateau. The second class of modified air field has a quench (or a plateau-quench). Quenching was simulated as a step drop in air temperature. The simulation showed that quenching can enhance online crystallinity, though fiber attenuation is reduced when quenching is used.

  • next generation modeling of Melt Blowing
    Industrial & Engineering Chemistry Research, 2011
    Co-Authors: E R Shambaugh, Dimitrios V Papavassiliou, Robe L Shambaugh
    Abstract:

    An advanced model has been developed for predicting the behavior of a fiber as it is formed in the Melt Blowing process. The model involves the simultaneous solution of the momentum, energy, and continuity equations. Crystallization effects are included. The model equations are solved numerically. As a bottom boundary condition in this solution, a “stop point” is assumed. The stop point is the point where (a) the fiber stress is zero, and (b) the air velocity and fiber velocity are equal. Predicted parameters include fiber diameter, velocity, temperature, stress, and crystallinity. The predicted results show that very little online crystallization takes place under typical Melt Blowing conditions.

  • Online measurement of fiber diameter and temperature in the Melt-spinning and Melt-Blowing processes
    Industrial and Engineering Chemistry Research, 2009
    Co-Authors: Vishnu T. Marla And, Robert L Shambaugh, Dimitrios V Papavassiliou
    Abstract:

    Online measurements of fiber temperature and diameter were made for both the Melt-spinning and the Melt- Blowing processes. The fiber temperature was determined by infrared thermography, and the fiber diameter was determined by high-speed photography. These measurements were then compared with predictions made with mathematical models for Melt spinning and Melt Blowing. There was good agreement between the models and the experimental results, and the agreement was best when heat-transfer correlations developed specifically for fine fibers (cylinders) were used.

  • effects of the polymer fiber on the flow field from a slot Melt Blowing die
    Industrial & Engineering Chemistry Research, 2007
    Co-Authors: Holly M Krutka, And Robert L Shambaugh, Dimitrios V Papavassiliou
    Abstract:

    Exxon slot Melt Blowing dies consist of dual, rectangular, converging jets and are used in the industrial Melt Blowing process to attenuate molten polymer fibers. The air flow creates a drag force that accelerates the polymer and rapidly reduces the fiber diameter. For previous experimental and computational fluid dynamics studies, the effect of the fiber on the air was assumed to be negligible. By including the fiber as a boundary in the computational domain, this assumption was tested. A modified version of the Reynolds stress model was used to simulate the turbulent air flow field. It was determined that the centerline air velocity (located halfway between the fibers) has an increased maximum due to the presence of the fiber. In addition, the turbulence in the flow field is dampened by the presence of the fiber. The jet spreading rate is higher halfway between the fibers than at the center of the domain, where the fiber is located. The air flow around the fiber is nonuniform, leading to varied shear st...

  • analysis of the temperature field from multiple jets in the schwarz Melt Blowing die using computational fluid dynamics
    Industrial & Engineering Chemistry Research, 2006
    Co-Authors: Holly M Krutka, Robe L Shambaugh, Dimitrios V Papavassiliou
    Abstract:

    Melt Blowing dies are used to manufacture fine polymer fibers rapidly. The Schwarz die is a type of Melt Blowing die that uses multiple jets to produce numerous polymer fibers simultaneously. Heated air flows through the air jets, each of which encloses a polymer capillary. The experimentally measured velocity and temperature fields from a Schwarz die can be reproduced using the k−e turbulence model. Six different multihole die geometries were simulated in three dimensions with this model. The geometries differed only in the spacing between the jets. The temperature field from the array showed significant variations from the temperature field from a single annular jet. The temperature field from the multihole dies decayed more slowly than that from a single annular jet. In addition, the temperature field from the different multihole geometries showed variations from each other, leading to observations relating to the interactions between multiple jets. As the spacing between the jets increased, the distan...

Robe L Shambaugh - One of the best experts on this subject based on the ideXlab platform.

  • Melt Blowing dies with louvers
    Industrial & Engineering Chemistry Research, 2015
    Co-Authors: Robe L Shambaugh, Joh D Krutty, Shaw M Singleto
    Abstract:

    A slot die is the most common type of spinning device used to make Melt blown fibers. A pair of louvers was installed in the air flow field of a Melt Blowing die. Air velocity measurements were taken in the presence of the louvers and in the absence of the louvers. In some experiments, the louvers were parallel with the airflow. In other experiments, the louvers were angled relative to the airflow at angles up to 6°. If higher air velocities can be achieved with louvers, then the Melt Blowing process can be improved.

  • modifying air fields to improve Melt Blowing
    Industrial & Engineering Chemistry Research, 2012
    Co-Authors: E R Shambaugh, Dimitrios V Papavassiliou, Robe L Shambaugh
    Abstract:

    An advanced model for Melt Blowing was used to predict the effects of modified air fields on fiber formation. The model, which was developed previously, involves the simultaneous solution of the momentum, energy, and continuity equations. Crystallization effects were included. The model equations were solved numerically. Simulations were done for two classes of modified air fields. The first class of modified air field has a plateau of constant velocity and temperature. For wide plateaus placed near the die face, the effect of the plateau is substantial. Fiber diameters are reduced (by up to two times) versus diameters for when there is no plateau. The second class of modified air field has a quench (or a plateau-quench). Quenching was simulated as a step drop in air temperature. The simulation showed that quenching can enhance online crystallinity, though fiber attenuation is reduced when quenching is used.

  • next generation modeling of Melt Blowing
    Industrial & Engineering Chemistry Research, 2011
    Co-Authors: E R Shambaugh, Dimitrios V Papavassiliou, Robe L Shambaugh
    Abstract:

    An advanced model has been developed for predicting the behavior of a fiber as it is formed in the Melt Blowing process. The model involves the simultaneous solution of the momentum, energy, and continuity equations. Crystallization effects are included. The model equations are solved numerically. As a bottom boundary condition in this solution, a “stop point” is assumed. The stop point is the point where (a) the fiber stress is zero, and (b) the air velocity and fiber velocity are equal. Predicted parameters include fiber diameter, velocity, temperature, stress, and crystallinity. The predicted results show that very little online crystallization takes place under typical Melt Blowing conditions.

  • analysis of the temperature field from multiple jets in the schwarz Melt Blowing die using computational fluid dynamics
    Industrial & Engineering Chemistry Research, 2006
    Co-Authors: Holly M Krutka, Robe L Shambaugh, Dimitrios V Papavassiliou
    Abstract:

    Melt Blowing dies are used to manufacture fine polymer fibers rapidly. The Schwarz die is a type of Melt Blowing die that uses multiple jets to produce numerous polymer fibers simultaneously. Heated air flows through the air jets, each of which encloses a polymer capillary. The experimentally measured velocity and temperature fields from a Schwarz die can be reproduced using the k−e turbulence model. Six different multihole die geometries were simulated in three dimensions with this model. The geometries differed only in the spacing between the jets. The temperature field from the array showed significant variations from the temperature field from a single annular jet. The temperature field from the multihole dies decayed more slowly than that from a single annular jet. In addition, the temperature field from the different multihole geometries showed variations from each other, leading to observations relating to the interactions between multiple jets. As the spacing between the jets increased, the distan...

  • temperature fields below Melt Blowing dies of various geometries
    Industrial & Engineering Chemistry Research, 2004
    Co-Authors: Ia D Tate, Robe L Shambaugh
    Abstract:

    Temperature fields were measured below two parallel, rectangular air nozzles. These are the types of nozzles that are commonly used in the Melt-Blowing process to produce fine polymer fibers. Each rectangular nozzle had a large length-to-width ratio, and the nozzles were closely spaced. Three types of nozzles were compared:  (1) a die where the jets meet at a 60° angle and the die tip was blunt, (2) a die with a 60° angle and a sharp tip, and (3) a die with a 70° angle and a sharp tip. Correlations were developed to predict the temperature fields below these die types.

Xinhou Wang - One of the best experts on this subject based on the ideXlab platform.

  • Influence of Processing Conditions on the Basis Weight Uniformity of Melt-Blown Fibrous Webs: Numerical and Experimental Study
    2018
    Co-Authors: Jingru Yang, Xinhou Wang
    Abstract:

    Basis weight uniformity of Melt-blown fibrous webs is attracting considerable interest because it directly affects the application performance of nonwovens. There are numerous studies which introduce factors of processing conditions on the basis weight uniformity based on their final applications. However, theoretical research is still scarce. This paper describes the numerical modeling (bead–viscoelastic element fibrous model) involving fibrous web structure generation and basis weight uniformity evaluation. The effects of four processing conditions, including velocity of air jet and suction, die-to-collector distance, and moving speed of collector, on the basis weight uniformity of the fibrous web were quantitatively analyzed. Additionally, computational fluid dynamics simulation was employed to study the air flow (including the suction) in the Melt-Blowing process. The simulated results were in good agreement with the experimental data. The numerical model was practical and could better be used to research the problems on fibrous web formation and structures

  • simulation and modeling of microfibrous web formation in Melt Blowing
    Industrial & Engineering Chemistry Research, 2016
    Co-Authors: Jingru Yang, Xinhou Wang
    Abstract:

    A novel method to predict accurately the formation of fibrous webs in the Melt-Blowing process is developed. When an image analysis technique is combined with the Fluent software, the fiber spatial position and consequent landing position on the moving collection screen are predicted. The results include the prediction of fiber deposition patterns in the resulting fibrous web. In addition, to verify the prediction quantitatively, the basis weight distribution and the variation coefficient of the basis weight for both the predicted and experimental fibrous webs are investigated. Comparison of the prediction with the experimental data suggests that the method captures the primary trends rather accurately, not only for the single-orifice experiment but also for commercial multiple-orifice production.

  • investigation of nanofiber breakup in the Melt Blowing process
    Industrial & Engineering Chemistry Research, 2016
    Co-Authors: Gajanan S. Bhat, Xinhou Wang
    Abstract:

    Nanofibers definitely hold a great advantage and can be applied in many areas because they have very high specific surface area. Recently, great attention is being paid to fabricate nanofiber nonwoven webs using Melt-Blowing technology. In this paper, Melt-blown nanofibers have been produced by multihole dies using two kinds of commercial polymers under different processing conditions. The average nanofiber diameters achieved were 780 and 810 nm, respectively. The fiber breakup, which was driven by surface tension when fiber diameters approached nanoscale, was investigated. The Rayleigh instability theory for a Melt-Blowing fiber was introduced and illustrated as the reason for fiber breakup. Both theory and experimental results reveal that the surface tension, polymer viscosity, fiber diameter, and Melt-Blowing-process conditions, such as air pressure and temperature, significantly influence the fiber breakup. This research gives a useful understanding for the formation of Melt-blown nanofibers and provi...

  • modeling Melt Blowing fiber with different polymer constitutive equations
    Fibers and Polymers, 2016
    Co-Authors: Xinhou Wang
    Abstract:

    The characteristics of molten polymer plays a major role in fiber formation in the Melt Blowing (MB) process. In this paper, the Maxwell model and two kinds of the standard linear solid (SLS) models in the bead-viscoelastic element model are proposed for Melt blown fiber formation simulation. The fiber diameter, velocity and stress are studied with these different constitutive equations of polymer. The trajectory path of fiber whipping is obtained using numerical simulation and compares with the actual fiber motion which is captured with a high-speed camera. The results present that the Standard Linear Solid Model (SLS) is better than Maxwell model to predict the Melt blown fiber’s characteristics under the same air drawing conditions, including fiber diameter, velocity and stress. The whipping motion of the fiber also can be well expressed by SLS constitutive model. The mathematical model with SLS model provides a clear understanding on the mechanism of the formation of microfibers during Melt Blowing.

  • numerical analysis of new modified Melt Blowing dies for dual rectangular jets
    Polymer Engineering and Science, 2014
    Co-Authors: Yudong Wang, Xinhou Wang
    Abstract:

    According to the aerothermodynamic analysis and turbulence characteristic analysis, there might be two main kinds of kinetic energy loss of the jets from rectangular nozzles for the blunt Melt-Blowing die. To reduce the energy loss, the new modified dies with stabilizing pieces are designed and compared with the blunt die. The air flow fields for the new dies are simulated using computational fluid dynamic technology, whereby the shear stress transport model is used for turbulence simulation. Three parameters (i.e., the velocity along the y-direction, the static temperature, and the turbulence intensity) are vitally important for producing fibers and thus are used to evaluate the performances of the slot dies. The simulation results reveal that the inner stabilizing pieces is helpful to decrease the negative velocity in the recirculation zone, enhance the downward centerline mean velocity, slow the centerline temperature decay, and make the air flow near the nose piece smoother. However, the external stabilizing pieces conduce only to increase the centerline velocity in the local area. POLYM. ENG. SCI., 54:110–116, 2014. © 2013 Society of Plastics Engineers

Holly M Krutka - One of the best experts on this subject based on the ideXlab platform.

  • effects of the polymer fiber on the flow field from a slot Melt Blowing die
    Industrial & Engineering Chemistry Research, 2007
    Co-Authors: Holly M Krutka, And Robert L Shambaugh, Dimitrios V Papavassiliou
    Abstract:

    Exxon slot Melt Blowing dies consist of dual, rectangular, converging jets and are used in the industrial Melt Blowing process to attenuate molten polymer fibers. The air flow creates a drag force that accelerates the polymer and rapidly reduces the fiber diameter. For previous experimental and computational fluid dynamics studies, the effect of the fiber on the air was assumed to be negligible. By including the fiber as a boundary in the computational domain, this assumption was tested. A modified version of the Reynolds stress model was used to simulate the turbulent air flow field. It was determined that the centerline air velocity (located halfway between the fibers) has an increased maximum due to the presence of the fiber. In addition, the turbulence in the flow field is dampened by the presence of the fiber. The jet spreading rate is higher halfway between the fibers than at the center of the domain, where the fiber is located. The air flow around the fiber is nonuniform, leading to varied shear st...

  • analysis of the temperature field from multiple jets in the schwarz Melt Blowing die using computational fluid dynamics
    Industrial & Engineering Chemistry Research, 2006
    Co-Authors: Holly M Krutka, Robe L Shambaugh, Dimitrios V Papavassiliou
    Abstract:

    Melt Blowing dies are used to manufacture fine polymer fibers rapidly. The Schwarz die is a type of Melt Blowing die that uses multiple jets to produce numerous polymer fibers simultaneously. Heated air flows through the air jets, each of which encloses a polymer capillary. The experimentally measured velocity and temperature fields from a Schwarz die can be reproduced using the k−e turbulence model. Six different multihole die geometries were simulated in three dimensions with this model. The geometries differed only in the spacing between the jets. The temperature field from the array showed significant variations from the temperature field from a single annular jet. The temperature field from the multihole dies decayed more slowly than that from a single annular jet. In addition, the temperature field from the different multihole geometries showed variations from each other, leading to observations relating to the interactions between multiple jets. As the spacing between the jets increased, the distan...

  • analysis of multiple jets in the schwarz Melt Blowing die using computational fluid dynamics
    Industrial & Engineering Chemistry Research, 2005
    Co-Authors: Holly M Krutka, And Robert L Shambaugh, Dimitrios V Papavassiliou
    Abstract:

    Melt-Blowing dies are used industrially to fabricate fine polymer fibers. The Schwarz die is a type of Melt-Blowing die that uses multiple columns of polymer orifices and associated air jets. This arrangement contrasts with the single column of orifices that is used in the slot, or Exxon, die. The experimental measurements of the air flow field from a Schwarz die can be reproduced using a k-e turbulence model. Six different multihole die geometries were simulated in 3D with this model. In comparison with the flow field of a single jet, the velocity maximums occurred closer to the die face for an array of jets. The spreading rates for the center jets of the multihole dies were similar to each other, and close to 0.5, while the spreading rate of a single annular jet has been observed to be close to twice this value. In addition, the differences in the air fields of the multihole geometries lead to observations concerning multiple jet interactions. The distance required for the inside column of jets to affec...

  • effects of temperature and geometry on the flow field of the Melt Blowing process
    Industrial & Engineering Chemistry Research, 2004
    Co-Authors: Holly M Krutka, And Robert L Shambaugh, Dimitrios V Papavassiliou
    Abstract:

    Converging plane jets are used commercially to produce polymeric fibers in the Melt Blowing process. The behavior of the air flow below the die face is critical for the production process. The die configuration can affect this flow field. Previous work has studied the effects of changing the angle of convergence of the two jets for blunt and sharp die faces, as well as the case of recess or excess (inset or outset) positioning of the sharp die nose for isothermal flow conditions. This study utilized a computational fluid dynamics approach that was validated through experimental data to investigate the effects of nonisothermal conditions on the air flow. The Reynolds stress model was used to simulate the turbulence, and the model parameters were calibrated with the experimental data. The behavior of alternative die designs was also correlated to the die configuration. It was found that, similarly to the isothermal case, the sharper the angle of convergence, the higher the mean air velocity under the die an...

  • effects of die geometry on the flow field of the Melt Blowing process
    Industrial & Engineering Chemistry Research, 2003
    Co-Authors: Holly M Krutka, And Robert L Shambaugh, Dimitrios V Papavassiliou
    Abstract:

    Sharp dies are often used commercially to produce polymeric fibers in the Melt-Blowing process. In these sharp dies, the flow field results from two similar converging plane jet nozzles with no space between the nozzles. This study utilizes a computational fluid dynamics approach that is validated through experimental data to investigate the effect of recess or excess (inset or outset) of the die nose on the flow field. The Reynolds Stress Model is used to simulate the turbulence, and the model parameters are calibrated with experimental data. The flow field downstream from the sharp die is found to exhibit (a) a merging region, which includes a maximum in turbulence intensity, and (b) a self-similar region. The behavior of alternative die designs is correlated to the die configuration. The more that the nose piece is recessed, the larger is the mean velocity under the die, but at the same time the turbulence becomes stronger.

Robert L Shambaugh - One of the best experts on this subject based on the ideXlab platform.

  • Online measurement of fiber diameter and temperature in the Melt-spinning and Melt-Blowing processes
    Industrial and Engineering Chemistry Research, 2009
    Co-Authors: Vishnu T. Marla And, Robert L Shambaugh, Dimitrios V Papavassiliou
    Abstract:

    Online measurements of fiber temperature and diameter were made for both the Melt-spinning and the Melt- Blowing processes. The fiber temperature was determined by infrared thermography, and the fiber diameter was determined by high-speed photography. These measurements were then compared with predictions made with mathematical models for Melt spinning and Melt Blowing. There was good agreement between the models and the experimental results, and the agreement was best when heat-transfer correlations developed specifically for fine fibers (cylinders) were used.

  • On-line Measurement of fiber motion during Melt Blowing
    Industrial & Engineering Chemistry Research, 2007
    Co-Authors: Jessica H Beard, Brent R Shambaugh, Robert L Shambaugh, David W. Schmidtke
    Abstract:

    A high-speed camera was used to record the motion of a fiber below both a Melt-Blowing slot die and a Melt-Blowing swirl die. These recorded images were processed to determine the frequency and amplitude of fiber motion during Melt Blowing. The operating variables investigated included polymer flow rate, air flow rate, polymer temperature, and air temperature. A crossover counting method was developed to determine the frequency of fiber motion. The frequencies determined from this counting method favorably compared with frequencies determined by taking fast Fourier transforms of the fiber displacement data. Experimental results for frequency and amplitude were compared to predictions from a three-dimensional mathematical model for the Melt-Blowing process.

  • Three-Dimensional Model of the Melt-Blowing Process
    Industrial & Engineering Chemistry Research, 2003
    Co-Authors: Vishnu T. Marla And, Robert L Shambaugh
    Abstract:

    A model has been developed that can predict the three-dimensional motion of a fiber as it is being formed below a Melt-Blowing die. The model involves the simultaneous solution of the momentum, energy, and continuity equations. The model equations are solved numerically with both Newtonian and viscoelastic constitutive equations. Predicted parameters include fiber attenuation, vibration frequency, vibration amplitude, temperature, and stress. The predicted results compare favorably with previously published experimental data.

  • investigation of gravity spun Melt spun and Melt blown polypropylene fibers using atomic force microscopy
    Journal of Applied Polymer Science, 2000
    Co-Authors: Anne De Rovere, Robert L Shambaugh, Edgar A Orear
    Abstract:

    The morphology exhibited in a polymer depends on the particular process and processing conditions used to shape and modify the polymer. This morphology has an important influence on the final polymer product (sheet, molded part, etc.). Ten years ago, atomic force microscopy (AFM) was applied for the first time on polymer materials. Since then, AFM has been used extensively on polypropylene (PP) surfaces, but still very little has been reported on the use of AFM for analyzing PP fibers. The purpose of our work was to show the modifications of (a) the morphology and (b) the microstiffness of PP fiber surfaces processed under different operating conditions. Three fiber production processes were used: gravity spinning, Melt spinning, and Melt Blowing. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 1921–1937, 2000

  • vibration and stability in the Melt Blowing process
    Industrial & Engineering Chemistry Research, 1993
    Co-Authors: Robert L Shambaugh
    Abstract:

    A model has been developed to predict the thermal and mechanical behavior of a polymer stream after it exits a Melt Blowing die. The model is a logical extension of the Uyttendaele and Shambaugh model for Melt Blowing. The present model, unlike the previous model, takes into account the fiber vibrations that become pronounced during high-velocity Melt Blowing. The model can be used to estimate the experimental conditions that will cause fiber breakage