Effects of the Polymer Fiber on the Flow Field from an Annular Melt-Blowing Die

Abstract

Annular air jets are used commercially to attenuate a polymer fiber in the melt-blowing process. As polymer is extruded from a small capillary, the air flow from the jet creates a drag force on the surface of the polymer. The result is a rapid attenuation of the polymer into a fine fiber. In the present work, computational fluid dynamics was used to examine the effect of the polymer fiber on the air flow field from an annular jet, which is a common configuration for melt-blowing dies. The effect of the polymer fiber on the air has often been assumed to be negligible in previous studies of melt blowing. The turbulence in the air flow was simulated using a modification of the Reynolds stress model. An important finding is that the polymer fiber has a dampening effect on the turbulence. In addition, the presence of the polymer leads to an increase in the jet spreading rate. As the inlet air flow rate was decreased relative to the polymer flow rate, the effect of the polymer on the air flow field was observed to become stronger.

Optimization of air flow field of the melt blowing slot die via numerical simulation and genetic algorithm

“…Therefore, we should focus the stagnation temperature on the centerline where fibers locate. Krutka13 did a deep research of the effect of fiber on flow field. He found the effect decreases as the distance from the die face increases so that it can be neglected at the far field.…”

Experimental Investigation of the Fiber Formation Process and Web Structures Using an Annular Meltblowing Spinneret

“…27,28 Subsequent investigations implemented computational methods to study the air flow in much greater detail than possible experimentally for both single-hole 29 and multihole annular air jets 30 and in the presence or absence of an imaginary fiber. 31 Most recently, computational investigations have examined airflow in modified annular jets, such as the introduction of a mid-stream "plateau" or a quench, 32 and modified nozzle shapes to increase the air speed contacting the emerging polymer jet. 33 Although the velocity and temperature fields where the molten polymer is drawn into a fiber are critical to understand, it is only a part of the puzzle of this very complex and dynamic process.…”

Study on airflow field and fiber motion with new melt blowing die

“…Some researchers have investigated different die geometries to optimize the airflow field below the die face to obtain smaller fiber diameter and better web uniformity. Shambaugh and coworkers did a series of work on understanding the airflow field in the melt blowing process. They first used numerical simulation to analyze the velocity and temperature fields and their effects on the polymer fiber for the melt blowing die airflow field.…”