Simulation of intra-cavity distribution mixing under the action of enhanced triangular rotor of twin-screw extruder
The intra-cavity mixing behavior under the action of a triangular rotor represents a typical mixing problem and has broad engineering application potential.In order to further improve distributive mixing,three enhancement ways were proposed in this paper,including increasing the edge length of the cams,changing cam shapes by perturbation method,and changing the cam topology.Allowing for the rotation periodicity of cams,using the mesh superposition technique,the numerical simulation models of the highly viscous fluid flow under the actions of different cam pairs were established and the instantaneous velocity fields were then solved.The investigations on the mixing dynamics were performed by using the self-developed Runge-Kutta scheme with fourth-order precession.The mixing behaviors were characterized in terms of Lagrangian coherent structures(LCS),interface stretch of tracer lines,and Poincaré cross section.When the edge length equals to 40 mm,two independent Komogorov-Arnold-Moser(KAM)islands turn up surrounding the left and right cams;when the cam edge length is increased up to 45 mm,the mixing mechanism inside the cavity is completely changed where single one KAM island wanders around the left and right sub-cavities along the quasi-periodic orbit of double loop connection orbit,consequently resulting in the best distributive mixing.Compared with changing cam shape,changing cam topology can achieve better mixing with lower power consumption,however,as the edge length of 40 mm does,the mixing mechanism where two independent KAM islands surround the left and right cams remains unchanged.
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