Study on Interlaced Yarn Part 3 : Air Flow in a Yarn Duct
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The flow field in a yarn duct of an interlaces is clarified by measuring pressure distributions on the yarn duct wall and flow velocity distributions near it. An enlarged interlacer similar to a practical interlacer has been manufactured on the basis that the flow fields in two similar interlacers in geometry are also similar in fluid dynamics. In this manner detailed measurements can be made and data with high accuracy can be obtained. Results are as follows:<br>(1) With regard to the axial direction of the yarn duct, the pressure <i>h<sub>s</sub></i> takes the maximum near <i>Z</i>=0 and the minimum near |<i>Z</i>|=1, where <i>Z</i> is the axial distance from the center of the air jet nozzle non- dimensionalyzed by the diameter of the yarn duct. The value of <i>h<sub>s</sub></i> gradually increases with |<i>Z</i>|, and is identical with the atmospheric pressure at |<i>Z</i>|=2. The above- mentioned tendency is independent of θ and <i>p</i> in the present experiment, where θ is the circumferential angle in the yarn duct from the center of the air jet nozzle and <i>p</i> is the air pressure in a rectification tank.<br>(2) The variation of <i>h<sub>s</sub></i> with respect to θ depends upon <i>Z</i>. In <i>Z</i>=0 the value of <i>h<sub>s</sub></i> is extremely large at θ=180 deg and reaches the minimum near θ=90, 270 deg. In <i>Z</i>=1 it shows a considerably small variation, and a negative value in almost all regions. In <i>Z</i>=2 it is almost constant and nearly equal to the atmospheric pressure.<br>(3) Compared to the air pressure in a rectification tank, the value of <i>h<sub>s</sub></i> is nearly equal to the atmospheric pressure in almost all parts of the yarn duct wall.<br>(4) The air jetting from the air jet nozzle radially spreads along the yarn duct wall after running against the wall opposite to the air jet nozzle. The air with a circumferential component of flow velocity flows along the curved wall, and two eddies are formed which are symmetric with respect to the plane through θ=0, 180 deg and rotate in opposite directions to each other. With increasing |<i>Z</i>|, the circumferential component of flow velocity diminishes and the axial component is dominant. The main flow moves from the periphery of the yarn passage to its center. With respect to the circumferential direction of the yarn passage, the flow is biased toward the semicircular region nearer to θ=180 deg.<br>(5) The present experiment shows that the air flow pattern in a yarn duct is independent of <i>p</i>.<br>(6) It is considered that the air jet causes not only opening and tangling behavior of a yarn in the region (|<i>Z</i>|< 1/2) where the jet directly runs against the yarn, but a yarn motion similar to rotation in the region (|<i>Z</i>|<1) where the circumferential component of flow velocity is relatively dominant.<br>(7) Since errors in manufacturing interlacers have an influence on the flow field in a yarn duct, they are considered to cause yarns with various characteristics even when the processing conditions are common among interlacers.
- Journal of Textile Engineering
Journal of Textile Engineering 43(2), 38-46, 1997-06
The Textile Machinery Society of Japan