Yoshiyuki Iemoto

Weft Insertion by Water Jet Part I : Flow Velocity and Configuration of the Jet in the Vicinity of the Nozzle Exit

For the final purpose of making clear a mechanism of weft yarn insertion in a water-jet loom, the flow and configuration of the jet in the vicinity of the nozzle exit have been analyzed by utilizing the matched asymptotic expansion technique. Since in the present analysis the flow field, the nozzle profile, and the weft profile have been idealized, the results cannot indicate the actual phenomena in a strict sense. However, the following results have been obtained. The flow is per turbed by using the small parameter (the reciprocal of the cube root of the Reynolds number). The decreases of the radius of the core-flow region, the jet-radius, and the acceleration of the flow velocity near the free boundary of the jet have been calculate as a function of the distance from the nozzle exit. In order to calculate in detail the weft-insertion force, the other region near the weft surface is to be taken into account.

Numerical simulation of airflow characteristics in the spinning zone at starting time of air-jet spinning machine

To clarify the formation mechanism of a source of yarn and to discuss the effects of supplied air pressure and exhaust air pressure on the fiber suction force and twist torque at the starting time of the spinning process in an air-jet spinning machine, we simulated, numerically, the three-dimensional airflow pattern without fibers in the spinning zone. Results obtained are as follows: High-speed air jetted through the starting nozzles into the yarn duct in the circumferential direction causes a swirl flow in the yarn duct and a negative pressure region near the center axis of the yarn duct. Hence, air and fibers at the fiber inlet are sucked through the processing duct into the yarn duct. A fiber bundle sucked into the yarn duct rotates, owing to the action of the swirl airflow, and twists the fiber bundle in the processing duct, hence generating a source of yarn. The fiber suction force takes a distribution with a peak against the supplied air pressure and is independent of the exhaust air pressure. The fiber twist torque increases monotonously with supplied air pressure.

Simulation of Melt Spinning of Nylon-6 Using the Finite Element Method

The properties of polymer melts are different from those of monomeric materials because polymer materials have crystalline and amorphous regions. In addition, polymer melts exhibit elasticity as well as viscosity. Therefore, the viscoelasticity, crystallinity and temperature of polymer melts must be considered for an accurate simulation of the melt spinning process for crystalline polymers. In this study, we simulated the melt spinning process of Nylon-6 by using the streamline-upwinding finite element method. The non-isothermal Phan-Thien Tanner model proposed by Sugeng and Phan-Thien was employed as a constitutive equation. We investigated the distribution of temperature and crystallinity on the free surface of the filament, and the filament diameter.The calculations were nearly independent of gravity. The primary normal stress increases and the filament diameter decreases with an increase of take-up speed. The filament diameter obtained by the non-isothermal flow simulation is smaller than that for the isothermal case, and the filament diameter depends on the crystallinity. The filament shape for a purely viscous fluid is the same as that for a viscoelastic one.

Velocity Distribution of Running Viscoelastic Yarn Subjected to Drawing

目的 一対のローラ間で定常的に延伸されながら走行する粘弾性糸の速度分布, ひずみ分布, 応力および引取所要時間を理論的および実験的に求め, 糸の送出速度および延伸比の影響を検討する.成果 (1) 埋込座標系での1次元積分型構成方程式から誘導した速度分布, ひずみ分布, 応力および引取所要時間は, 粘弾性糸のクリープコンプライアンス, 送出速度および延伸比で定まる.(2) ポリエチレンテレフタレートモノフィラメント糸に対する速度分布, 応力および引取所要時間の計算値は実測値と一致する.(3) 応力は, 送出速度および延伸比が増すと増加する.(4) 計算および実測による速度分布曲線はともに上に凸の単調増加を示すが, 実測値は計算値より低くなる.(5) 速度勾配の計算値は延伸比とともに増加する.なお, 速度勾配は実測値の方が計算値より大きくなる.(6) 引取所要時間は, 延伸比の増加に対し単調に減少し, その傾向は低送出速度の場合に顕著となる.

Study on Interlaced Yarn:Part 4: Yarn Posture in Interlacer, and Relation between Yarn Positions and Number of Tangles

目的 インターレーサ内の糸の運動を明らかにするための基礎実験として, 加工時の糸をスチールカメラで複数回にわたって撮影し, 糸の位置をコンピュータで統計的に処理することにより, インターレーサ内の糸の姿勢について解析する.又, 糸の位置と交絡数の関係についても検討する.成果 (1) 糸の姿勢の解析には, 糸道断面を6個のエリァに分割し各エリァにおける糸の位置を糸軸方向に調べる方法を用いた.その結果, 本研究範囲内ではインターレーサ内の糸の姿勢に際立った特徴は見られない. (2) 空気圧が2～4kg/cm2の範囲では, 糸は空気噴流軸の左右に均等に位置し頻繁に噴流を横切る.しかし, 空気圧が小さいために糸を充分開繊または交絡させることができない.空気圧が5～7kg/cm2と大きい場合, 糸は噴流軸の片側に位置し噴流を横切る回数は少ない.すなわち, 空気圧の小さい範囲と大きい範囲での交絡数の少ない原因は異なる.従って, 空気圧の変化だけでなく糸の運動も考慮すれば, 空気圧が4.5kg/cm2のとき最大となる交絡数の変化を説明できる. (3) 糸速の増加と共に糸の位置に偏りが生じ, 糸が空気噴流を横切る回数は減少する.交絡数と糸速が単純に反比例関係で表されないのはこれが原因であると考えられる. (4) フィード率の増加と共に糸張力が減少し, 糸が空気噴流を横切る回数は減少するため, 交絡数も減少する.フィード率が小さい場合, 糸の運動は糸道の中心に制限されるため頻繁に噴流を横切るが, 糸張力が大きいので交絡部はあまり生じない.従って, フィード率がおよそ1%で交絡数は最大となる.

Flow of Viscoelastic Fluid in a Curved Pipe

The flow rate of a steady flow of viscoelastic fluid under a constant axial pressure gradient in a toroidal pipe of circular cross-section is analytically solved with the White-Metzner constitutive equation by a perturbation method. It is examined how the shear thinning viscosity and elasticity affect the flow rate of the fluid at high shear-rate to which former analyses could not be applied.The analysis shows that the characteristics of the flow in a curved pipe are determined not only by the Dean number but also by the non-dimensional value We; /√ where We; is the Weissenberg number and R is the ratio of the toroidal radius to the pipe cross-sectional one. The results calculated for the ratio fr; of the flow rate in a toroidal pipe to that in a straight pipe under the same axial pressure gradient at low Reynolds number are as follows:(1) In the case of the Power law fluid in which We; is zero, fr; decreases with increment of the Reynolds number Re; and with decrement of the viscosity index n representing the shear thinning viscosity. Thus, the pipe resistance in a curved pipe is higher than that in a straight one.(2) The larger We; gives the larger fr; and thus the smaller pipe resistance.(3) Large Re; and small n give large increment of fr; with increasing We; .(4) The effect of the elasticity index s, representing the shear thinning elasticity, on fr; is insignificant unless n is small.