Simulation and Optimization of Dry Spinning Processes

Simulation tool for high-quality filaments

The industrial applications of dry spinning processes range from textiles and nonwovens to lightweight components. In a typical dry spinning process, a diluent polymer mixture is extruded through the nozzles of a spinning plate and aerodynamically dried in a spinning duct. The solidified fibers are taken-off at the end of the duct and thereby stretched.

In several years of research and development, we have created a simulation tool that handles dry spinning processes with hundreds or thousands of fibers. It covers both the full interaction of all fibers with the surrounding gas flow and the diffusion of the diluent in each individual fiber.

The result is both the complete aerodynamics of the gas flow (velocity, temperature, diluent distribution) as well as all relevant state variables along the fiber (diameter, speed, temperature). Thereby, the diluent concentration is resolved radially in the cross sections of the fibers.

 

Cost Savings through Simulation

The simulations performed at our institute enable an in-depth analysis of the processes and their optimization through variation of the process and geometrical parameters. For example, the duct geometry can be optimized to reduce turbulence and improve the quality of the fibers. In particular, the upscaling from the laboratory to industrial scale can be achieved by the use of simulations. Significant cost savings are realized by reducing or avoiding expensive structural modifications.

Schematic model of a dry spinning plant
© Fraunhofer ITWM

The filaments are blown dry with air or gas while falling through the spinning duct, removing the solvent. Picture: Schematic model of a dry spinning plant.

Video Dry Spinning Processes at our Institute

German with English subtitles

Customer Example: Ceramic Manufacturer BJS Ceramics and Composites GmbH

BJS Ceramics and Composites manufactures components for aerospace and industrial applications from high-performance SiC composites. We work with them on the project.

Die Simulation erfasst die Konzentration des Lösungsmittels in jeder einzelnen Faser.
© Fraunhofer ITWM

Die Simulation erfasst die Konzentration des Lösungsmittels in jeder einzelnen Faser.

Three Questions for Dr. Michael Rothmann, Head of Development, BJS Ceramics GmbH, Gersthofen

What distinguishes your company? What does BJS Ceramics do? 
At BJS Ceramics, everything revolves around SiC fibers, a material that performs where other materials fail. Components made of SiC fibers can be used at 1500°C under aggressive conditions. One of many areas of application for this material is the hot gas range of aircraft turbines. By substituting metals the efficiency can be increased and the emission of CO2 and nitrogen oxides can be reduced. BJS thus makes an important contribution to achieving the EU's climate targets.

 

How is the cooperation with the Fraunhofer ITWM structured?
The cooperation is very practice-oriented. We discuss the questions on site directly at the plant. The experts from the ITWM then develop a solution and present it. In a first iteration, the basic suitability of the chosen approach is checked. After this proof-of-concept, the model is further refined before it is used. During the collaboration, we exchange information at regular meetings. This ensures that new questions can be quickly addressed and incorporated.

 

What is so special about the simulation? What is innovative?
In our current collaboration, we were able to simulate the entire spinning process for the first time. This was made possible by combining several simulation methods. This gives us an insight into previously inaccessible parts of the process. These results will enable us to carry out more targeted process optimization in the future and shorten our development cycles.