A Study of the Airflow and Fiber Dynamics in the Transport Chamber of a Sifting Air-laying System: Part 1

The structural architecture of air-laid webs produced from short fibres is largely dependent on the manner in which fibres are assembled together during the web formation process. An improved understanding of the behaviour of fibres during air-laying is essential to provide a basis for more effective engineering of the structure and properties of resulting fabrics. This two part paper presents the results of a preliminary experimental study of the airflow and the fibre dynamics in a sifting air-laying process using LDV and high-speed photographic techniques. In Part 1 of the paper the airflow characteristics are investigated using Laser Doppler Velocimetry. In a commercially representative sifting air-laying machine it was established that the air velocity varies along the length and the height of the transport chamber. The variation is markedly increased by the rotation of the blades in the dispersing zone. Generally, the air velocity was found to increase from the top to the bottom of the transport chamber. With the rotating blades in operation the trend in the airflow velocity was characterised by a ‘V’ shaped profile along the length of the chamber and was independent of the height of the chamber. (Part 2 of this paper will appear in the Fall, 2000 issue of the International Nonwovens Journal.)