The primary airflow system (PAS) in Spunbond systems involves the use of very high velocity, and often supersonic, air jets. Air is pumped into the slot from a compressed air system. Appropriate designs of the PAS can result in significant energy savings. To demonstrate the applicability of Fluent's flow modeling software for designing PASs, such a system with an inlet pressure of 45 psig is analyzed. Figures A and B show predicted Mach number contours and velocity vectors in the PAS. These results demonstrate the ability of the FLUENT to capture flow separation in the presence of blunt edges. FLUENT can be used to optimize the design of the tangential jet entrance to provide a smooth expansion, thus eliminating the need to "cut metal".

Figure A - Contours of Mach number in the primary airflow

Figure B - Velocity vectors in the primary airflow system

Process layout for spunbond systems