かみ合い型同方向回転二軸スクリュ押出機のスクリュエレメントの押出特性に関する実験的研究
An Experimental Study on the Pumping Characteristics of Screw Elements for an Intermeshing Corotating Twin-screw Extruder
王 寧和・酒井忠基・橋本憲明
Wang, Ning He / Sakai, Tadamoto / Hashimoto, Noriaki
A visual study on the pumping characteristics of screw elements for an intermeshing co-rotating twin-screw extruder was conducted by using polystyrene melt as a classic non-Newtonian fluid. Here the output was regarded as the sum of drag flow and pressure flow based on the previous theoretical and experimental studies for single and twin-screw extruders. Therefore the relationship between the output and pressure gradient for a given screw geometry was approximately expressed as a linear dimensionless form which contains two dimensionless constants, the so-called pumping-characteristic parameters related to the element geometry and degree of departure of the used fluid from the Newtonian fluid.
The pumping-characteristic parameters for right-handed flight screw elements (RF) with leads of 0.938 D and 0.703 D, neutral kneading disk (NK) and blister ring (BR) were experimentally determined, where both the NK and the BR are regarded as the special forms of the screw elements without generating drag flow. Moreover the effect of the clearance between the screw and barrel on its pumping characteristics, where the right-handed flight screw element with lead of 0.938 D as an example was also observed. The results indicated that the expression of the linear relationship between the dimensionless output and dimensionless pressure gradient for each of the used screw elements is a good approximation. It was also found that the clearance in the range used here greatly affects the pumping characteristic of the RF, and that the latter should not be neglected for predicting the pumping characteristics or extruding and conveying capacities of the RF as well as the screw combination including its elements.
Key words: Twin-screw extruder / Visualization / Pumping characteristic / Polystyrene / Filling length