Fibre orientation anisotropy profile over the thickness of a headbox jet
2004 (English)In: Journal of Pulp and Paper Science (JPPS), ISSN 0826-6220, Vol. 30, no 8, 217-221 p.Article in journal (Refereed) Published
The fibre orientation anisotropy at various levels of the jet from a model headbox has been investigated. Stiff nylon fibres, 3 mm long, were added at extremely low concentrations to make it possible to observe also the centre of the jet. This meant that fibre interactions, such as floc forming, could not take place. Transparent, parallel walls enclosed the jet where fibre orientation was measured. A thin laser sheet illuminated the jet from the side and a video camera captured the light reflected perpendicularly from the fibres. Using image analysis, the orientation of the fibres was evaluated. A central vane was mounted in the headbox nozzle so the effects of the vane wake could be studied. The results show that the effect a the boundary layers, at the walls of a headbox and at the surface of a vane, was to locally reduce fibre orientation anisotropy. Depending on the vane tip shape, fibre orientation anisotropy could be additionally decreased. Overall, the fibre orientation anisotropy was weakly affected by changes inflow rate and strongly dependent on the contraction ratio in the nozzle; low speed and large contractions produced more anisotropic orientations.
Place, publisher, year, edition, pages
2004. Vol. 30, no 8, 217-221 p.
orientation, fibers, anisotropy, profiles, head boxes, jets, nozzles, image analysis, machine design
Paper, Pulp and Fiber Technology
IdentifiersURN: urn:nbn:se:kth:diva-41200ISI: 000224327100002ScopusID: 2-s2.0-20344363667OAI: oai:DiVA.org:kth-41200DiVA: diva2:443598
QC 201109262011-09-262011-09-232011-09-26Bibliographically approved