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

Ying Yang,Yongchun Zeng

doi:10.3390/polym13050719

Abstract

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.

Highlights

Due to it becoming a popular method due to its application on producing highefficiency air filters in industry [1,2,3,4], melt-blowing technology has been of increasing interest in recent years owing to the development of nanotechnology [5,6,7,8,9]
To better control the fluctuating airflow field and to achieve a more stabilized pattern of fibre oscillation, the studies of the aerodynamics and fibre motion pattern in the melt-blowing airflow field are of great importance
The result of the turbulence intensity showed that the turbulence intensity near the nozzle exit (2.5 mm < z < 12 mm) for the nozzle with the outer-director was of the lowest value among the conditions measured, while the turbulence intensity for the nozzle with the inner-director was considerably larger than that of the nozzle with the inner-director

Summary

Introduction

Due to it becoming a popular method due to its application on producing highefficiency air filters in industry [1,2,3,4], melt-blowing technology has been of increasing interest in recent years owing to the development of nanotechnology [5,6,7,8,9]. During the melt-blowing process, polymer melts are attenuated into micro/nanofibrous nonwovens with the help of high-speed hot air jets [10]. The melt-blowing slot-die, which contains a nozzle with a pair of slots to eject the two inclined hot air jets, is most commonly used to rapidly stretch the molten strand of polymer. The complex turbulent airflow field of melt-blowing, makes it difficult to fully reveal the underlying mechanism. The melt-blowing airflow field has been studied by researchers for decades and the effects of air turbulence on the fibre motion remain elusive. To better control the fluctuating airflow field and to achieve a more stabilized pattern of fibre oscillation, the studies of the aerodynamics and fibre motion pattern in the melt-blowing airflow field are of great importance

Methods

Results

Conclusion