The aerodynamical spinning process of the company Woltz is used for producing glass wool.
© Fraunhofer ITWM
After the molten polymer mass exits the spin packet, the spinning process becomes the real function defining step in the production process of fibers and filaments. The spectrum of application ranges from staple fibers and nonwovens to industrial textiles.
The spinning process mechanically or aerodynamically accelerates the fibers to the required spin speed. The process quality depends most of all on the regularity of the fiber characteristics and the productivity.
In recent years, a series of research activities at Fraunhofer ITWM have provided the foundation for a comprehensive simulation of such spinning processes. The filament models based on the Cosserat theory, are based on a one-dimensional balancing of mass, impulse and energy along the filament for string models and additionally, the rotary angular momentum for rod models.
The surrounding air flow produces a force on the filament and effects a thermal exchange with the filament. On the basis of analytical and experimental findings, ITWM has developed a universally applicable model for aerodynamic forces.
The retroactive effect on the flow is based on the general »action equals reaction« principle. Homogenization conducts this to linear momentum and energy sources in the flow, realizable as UDF in flow tools like FLUENT.
The result of the iterative linkage of fiber dynamics in MATLAB and the flow dynamics in FLUENT is a tool to simulate the entire interplay within the spinning process.This simulation principle has been used in cooperation with industry partners for various spinning processes. An aerodynamic spinning process is used by the Woltz Company in the production of fiberglass wool. In this process, the extrudate is first distributed onto a rotating disk as a glass film and then pressed out by centrifugal force through ten thousand holes and frayed out in a stream of air created by a hot gaseous flow near the disk and a surrounding curtain of cold air.
The simulations demand a high precision coupling due to the aerodynamically determined filament curves as well as the coupling with the glass film on the inside of the rotor. The aim of the optimization process is the most suitable integration of the various throughputs per hole of the different rows and the significantly higher spinning speed on the upper rows as compared to the lower rows.
Type of Project: ZIM Project
Project Partner: Woltz GmbH
Fraunhofer Institute for Industrial Mathematics ITWM