ツインワイヤーフォーミングシューのコンピューター解析

抄録

Twin wire formers have many advantages like a compact structual design and good sheet formation over ordinary Fourdrinier machines.
They, however, tend to give less one pass retention especially with regard to fine fraction of the incoming stock, which is not favorable to some kinds of papers like a LWC base.
In usual operations of twin wire formers, the dewatering rate at the first part of a forming shoe is so high that it is supposed to be one of the reasons of unfavorable fiber losses. Therefore, it seems to be possible to improve fine fiber retention without losing the overall dewatering efficiency at the forming shoe, by modifying the present round shoe profile to one which allows nearly a constant dewatering rate over its whole length.
At first, the dewatering resistance coefficient at the shoe is calculated from the observed dewatering rate in a normal machine operation, together with the theoretical consideration on filtration and thickening of fiber suspension. Then, using that value, the shoe profile which gives a constant dewatering rate in its whole length, is calculated by computer simulation.
As the result, following is obtained.
R=-6.667L+12.0
R : radius of curvature
L : surface length on the shoe
It means that the radius of its curvature decreases from ten meters in the begining to two meters at the end by an arithmetical progressional mode.
Though there are some other facters to be taken into consideration, we believe that this kind of simulational approach will lead to a new concept on designing the shoe profiles of twin wire formers, and probably combination formers.