Influence of design on dispersive mixing performance in an axial discharge continuous mixer—LCMAX 40

Abstract

The axial discharge continuous mixer combines the features of a continuous mixer and a twin screw extruder, expanding the flexibility of this compounding machine. In this work we analyzed the influence of rotor design on the dispersive mixing performance of a LCMAX 40 unit. Specifically we looked at various arrangements for the pushing and counter pushing units in the design of the LCMAX 40. A fluid dynamics analysis package-FIDAP, based on the finite element method, was used to model the flow behavior of a power law model fluid under different pressurization conditions. Dispersive mixing efficiency was q u a n a e d in terms of shear stresses and elongational flow components generated in the flow field. We found that the counter-pushing unit generally contributes more in building up high shear stresses. However, the generation of elongational flow components, which is beneficial for dispersive mixing, is not solely dependent upon the pushing-counter pus-configuration but rather on the overall rotor geometry. We found that the maximum number of counter-pushing units in the rotor design of the LCMAX 40 should not exceed two in order to provide adequate material pumping. Rotor designs with alternathg arrangements of pushing and counter-pushing units provide overall better dispersive mixing conditions. 936 POLYMER ENGINEERING AND SCIENCE, JUNE ISM, Vol. 38, No. 6 m. 1 . Rotor geometry for inal E M A X 40 (PPPX).the 0%-Fg. 2. Mesh designs for the sequential geometries of a quarter cycle (1 5" angle increment).

Strain mode of general flow: Characterization and implications for flow pattern structures

“…This is common for the conveying screw of extruders and many types of kneading elements, such as kneading disks, rotor elements, screw mixing elements, and so on. [5][6][7][8][9][10][11]15,[17][18][19][20]22,28,34,37,38 To observe this, Figure 2 shows the distribution of the magnitude of the strain rate, ffiffiffiffiffiffiffiffiffiffiffi D : D p , at the cross section B indicated in Figure 1. At the clearances between the screw-tips and the barrel surface, and the gap between two screws, ffiffiffiffiffiffiffiffiffiffiffi D : D p takes values larger than 600 (1/s), which is consistent with the circumferential shear rate of 460 (1/s) estimated from the screw rotation speed of 200 rpm.…”

“…8,9,[17][18][19][20][21][22] In mixing devices for highly viscous fluids, like polymers, the largest strain rate is achieved in narrow gap regions, which are the clearance between the screw/rotor tips and the barrel surface, and the gap between two screws/rotors in twin-shaft machines. Thus, it is usually the case the condition (1) is satisfied.…”

Entropy Time Evolution In A Twin-flight Single-screw Extruder And Its Relationship To Chaos

“…In our group we carried out three dimensional, isothermal flow simulations for various batch and continuous mixing equipment [19][20][21][22][23][24][25][26].…”

Capturing the Efficiency of a Melt-Mixing Process for Polymer Processing

“…λ MZ is zero when the flow is purely rotational, 1/2 when it is simple shear flow, and unity when there is no rotation (elongation flow). λ MZ has been calculated for the shearing disks of a twin-screw extruder (Li and Manas-Zloczower, 1994), a twin-rotor mixer (Yao and Manas-Zloczower, 1998), the conveying element of a twin-screw extruder (Cheng and ManasZloczower, 1998), and the kneading disks of a twinscrew extruder (Cheng and Manas-Zloczower, 1997). derived a strain-rate type identifier (11) which uses the invariant of the strain-rate tensor instead of using the vorticity tensor to determine the flow regime.…”