Analysis and Optimization of a Texturing Nozzle

In machines for the production of carpet fibers, the filaments are first stretched over heated galettes, accelerated subsequently in one or more air shafts by diagonally injected air flows, and finally joined in a lamellar channel for frilling. In order to optimize this well-functioning process, it is the objective of our project to examine the air flow in the so-called texturing nozzle in detail. Thus, the nozzle can be improved with respect to:

• air consumption,
  
• tensile load of the filament
  
• and twist effects.

The air flow in the texturing nozzle can be described by the conservation equations for mass, momentum and energy, combined with the ideal gas equation. This leads to the compressible Navier-Stokes equations. In the nozzle, the string of filaments is represented as a cylindrical dome, in order to simplify the geometry.

The movement of the filament is accounted for by the given wall velocity at the surface of the filament. Boundary conditions are the atmospheric pressure at the cross-section of the entrance point of the filaments, the temperature and pressure of the air flow and at the cross-section of the exit of the filaments.

The turbulence effects, which are important due to the high flow velocities of this transonic flow and the high Reynolds numbers, are accounted for by a special turbulence model. Start-up or other instationary effects are less important, therefore only stationary states of the flow are computed here.

Evaluating the Parameter Study

The three-dimensional computations were carried out with the commercial software package CFX. In order to evaluate the different nozzle geometries, a parameter study was carried out with respect to:

• variations of the roughness of the surface, 
• the filament velocity, 
• the filament diameter 
• and the temperature and pressure of the air flow.

The results were evaluated with respect to the optimization parameters air consumption, tensile load of the filament and twist effects and will be used for the improvement of the process parameters and the nozzle geometry in cooperation with our industrial partner.

In the figure, the particle paths for two slightly modified nozzle geometries are visualized, in order to show the different twist strength of the filaments.

Type of Project: Industry Project
Project Partner: NEUMAG, Neumünster