Model of the Yarn Twist Propagation in Compact Spinning with a Pneumatic Groove

Compact spinning with a pneumatic groove utilises the transverse air force and mechanical force of the pneumatic groove to condense the fibre bundle in order to eliminate the spinning triangle. This paper analyses the twist resistance moments and torsion moment in the process of twist propagation. Results from this research confirm that the twist propagation is affected by the spinning tension, the negative pressure in the air suction pipe, the related yarn properties (the yarn diameter, yarn twist, and the torsion rigidity of the yarn), and the related structure parameters of the pneumatic groove roller (the friction coefficient between the pneumatic groove and the fibre bundle, the number of round pores, the diameter of the round pore, the distribution rule of round pores in the condensing zone). The twist propagation model determines the critical condition of spinning a compact yarn, characterised by the critical mean pressure (i.e. corresponding to the critical negative pressure in the air suction pipe). The higher the yarn twist, the higher the torsion rigidity of the yarn, and the lower the spinning tension required, the higher the critical mean pressure.