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Modelling the dynamics of flexible and rigid fibres

Kondora G., Asendrych D.

Chemical and Process Engineering

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2013

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Vol. 34, nr 1

87--100

EN

A particle-level simulation technique has been developed for modelling fibre suspension flow in a converging channel of a papermachine headbox. The fibre model is represented by a chain of elements connected together. The model was verified by the simulation of rigid fibre dynamics in a simple shear flow. The period of rotation was found to be in a very good agreement with theory and reference data. The model was then employed to simulate fibre motion in a converging channel of a papermachine headbox. Fibre suspension motion was resolved using two-step procedure. Velocity field was calculated by means of a commercial CFD code ANSYS Fluent with RSM turbulence model applied and used as an input to the in-house code allowing to simulate fibre dynamics. Results of the calculations were used to construct the fibre orientation probability distribution (FOPD) which was found to be consistent with available experimental data.

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Fibre dynamics in the revolving-flats card. Part II An investigation into the opening, individualisation, orientation and configuration of fibres during short-staple carding

Dehghani A., Lawrence C. A., Mahmoudi M., Greenwood B., Iype C.

Autex Research Journal

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1999/2000

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Vol. 1, no. 2

78--87

EN

High-speed photography was used to investigate the state of fibres during the short-staple carding process. Image processing was employed to investigate the flow uniformity and the degree of opening and fibre individualisation of the fibre mass. The results showed that there is a considerable mass flow variation at the taker-in stage and at the back of the cylinder. Due to the carding action between the cylinder and the revolving flats, most tuftlets are separated into individual fibres, but some remain as micro tuftlets and are transferred to the doffer. With the increased discretisation the fibre mass becomes more uniformly distributed at the front of the cylinder. However, on the doffer the mass flow variation increases, which suggests that the transfer is not a uniform action. The angle of orientation of fibres was measured at the taker-in, at the front of the cylinder after the revolving flats and at the doffer stage. It was found that the fibres are highly orientated at the front of the cylinder. However, after the transfer region the degree of orientation of the fibres on the doffer decreases. In order to establish an understanding of the state of individual fibres, the change in the crimp level of fibres during the process was studied. It may be assumed that crimp level is directly related to the forces applied to the fibres. The results showed that the fibres at the front of the cylinder are subjected to more tension as compared to the fibres at the taker-in stage. A study was also carried out on the effect of the boundary layer around the cylinder by directly measuring the speed of individual fibres at the front of the cylinder. This study showed that the majority of the fibres are hooked to the cylinder wires and travel at the speed of the cylinder surface.

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Fibre dynamics in the revolving-flats card. Part I A critical review

Lawrence C. A., Dehghani A., Mahmoudi M., Greenwood B., Iype C.

Autex Research Journal

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1999/2000

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Vol. 1, no. 2

64--77

EN

The last several decades have seen significant developments to the revolving-flats card and much research has been published on the fundamentals of the carding process. There are still, however, contradictions in the detailed explanation of fibre behaviour during carding and in the effectiveness of certain developments widely accepted as beneficial. This paper presents a critical review of the literature concerning the way fibre mass is disentangled into individual fibres to form a card sliver and the effectiveness of principal machine components. Areas are indicated where further research is necessary to resolve contradictory views and further the understanding of the process.