Application of Network Analysis to Flow Systems with Alternating Wave Channels: Part A (Pressure Flows)
Sprache des Titels:
Englisch
Original Kurzfassung:
Wave-dispersion screws have been used industrially in many types of extrusion processes,
injection molding, and blow molding. These high-performance screws are constructed by replacing
the metering section of a conventional screw with a melt-conveying zone consisting of two or more
parallel flow channels that oscillate periodically in-depth over multiple cycles. With the barrier flight
between the screw channels being selectively undercut, the molten resin is strategically forced to flow
across the secondary flight, assuring repeated cross-channel mixing of the polymer melt. Despite the
industrial relevance, very few scientific studies have investigated the flow in wave-dispersion sections
in detail. As a result, current screw designs are often based on traditional trial-and-error procedures
rather than on the principles of extrusion theory. This study, which was split into two parts, was carried
out to systematically address this issue. The research reported here (Part A) was designed to reduce
the complexity of the problem, exclusively analyzing the pressure-induced flows of polymer melts in
wave sections. Ignoring the influence of the screw rotation on the conveying characteristics of the
wave section, the results could be clearly assigned to the governing type of flow mechanism, thereby
providing a better understanding of the underlying physics. Experimental studies were performed
on a novel extrusion die equipped with a dual wave-channel system with alternating channel depth
profiles. A seminumerical modeling approach based on network theory is proposed that locally
describes the downchannel and cross-channel flows along the wave channels and accurately predicts
the pressure distributions in the flow domain. The solutions of our seminumerical approach were,
moreover, compared to the results of three-dimensional non-Newtonian CFD simulations. The results
of this study will be extended to real screw designs in Part B, which will include the influence of the
screw rotation in the flow analysis.