Air Drag of Monofilament Yarn in Confined Jet

Abstract

Air drag force on a nylon monofilament yarn in a confined jet was measured as a basic study for operating yarn by airflow, for example; for weft-insertion, for holding the yarn end, for adjusting yarn tension and for drawing yarn into a hollow spindle. The relative velocity of airflow around a yarn was expanded up to 300 m/s. Previously, this had been investigated up to 100 m/s. Both the supplying air pressure and combinations of nozzles and pipes changed diffusion of the flow in a pipe. Air drag force increased extremely if the primary stream acted on the yarn directly when the jet from the nozzle was directed at very high speed (around sonic velocity). Yarn was often stuck inside the pipe by the airflow when very thin pipes were used. When this occurred, air drag force was reduced to half. The air drag coefficient Cf for monofilament yarn has been arranged using the radius Reynolds number, Rea, for suction flow with lower than 100 m/s. The formula, Cf = KRea-n, has been applied for suction flow under 500 in Rea. Cf could be arranged in the same manner for annular jet or confined jet if airflow acted on a yarn in the pipe uniformly. This formula, then, is also available even for very high velocity over 100 m/s. According to these results, we were able to calculate air drag force on monofilament yam. We anticipate applying this to the other kinds of yarn, and expect air power savings and improvement in yarn operation.