Influence of process parameters on properties of open-end and core-sheath friction spun acrylic yarns

The present paper is concerned with the influence of opening roller speed, difference in drum speed and suction air pressure on properties of acrylic open-end and core-sheath friction spun yarns. The results show that opening roller speed and suction air pressure have significant influence on properties of open-end friction spun yarns. In the case of core-sheath yarns, suction air pressure has influence on yarn tenacity and hairiness. However, yarn unevenness and imperfection are not significantly influenced by experimental variables. The results also show that core-sheath friction spun yarns have significantly higher yarn tenacity, modulus and work of rupture and have a lower level of yarn unevenness, imperfections, hairiness, and breaking elongation than open-end friction spun yarns.     

Friction spinning machine variable and yarn structure: Configuration of fibres in yarn in relation to machine variables

This article reports detailed study on the impact of some DREF-III machine variables (i.e. opening roller speed, suction air pressure and difference in drum speed) and sliver feeding positions on configuration of fibres in the yarn. It has been observed that percentages of leading and trailing hooks are significantly influenced by the feeding position of sliver. The machine variables also found to have significant influence on fibre configuration in most of the cases. The configuration of fibres is found to be controlled by air flow characteristics inside the duct and by landing behaviour of fibres on the spinning drums. In addition, it has been found that the machine variables have least impact on configuration of core fibres.     

Optimisation of fluid flow phenomena inside transport duct of a DREF‐III friction spinning machine. Part III: CFD approach

The present paper is Part III of a series of papers dealing with the air‐flow inside the transport duct of a DREF‐III friction spinning machine. The design of the transport duct used in a DREF‐III friction spinning machine has been modified and improved. The air‐flow analysis inside the transport duct was carried out using the computational fluid dynamics (CFD) software FLUENT after creating the transport duct geometry in the geometrical model software ‘GAMBIT’. The boundary conditions namely inlet, outlet, moving wall and wall were specified for the transport duct in GAMBIT and were then exported to FLUENT, where the pressure and velocity values were specified. The simulations were then done using k‐? model for turbulent flow. FLUENT solves the basic fluid dynamics equations namely the energy and momentum equations along with the additional equations. Air‐flow behaviour has been simulated in the various modelled modified transport ducts. Slots were created near the inlet and they were given an inclined profile in order to reduce the reverse flow by guiding the air‐flow. The transport duct with one pair of slots at 30° angle was finally selected based on techno‐economic aspects. The physical properties of finer and coarser count yarns made from the modified as well as the conventional transport duct were compared for assessing the enhancement of properties with transport duct modification.     

网孔罗拉集聚纺纤维集聚区内气流流动状态分析

网孔罗拉集聚纺纤维集聚区构建了三维模型,采用流体计算软件Fluent模拟了气流在该三维模型内的流动状态,并基于数值模拟结果分析了气流吸聚槽始端位置对纤维集聚区内气流流动状态的影响。经分析认为当气流吸聚槽始端与牵伸钳口线对应时,在纤维集聚区内的气流流动速度较高,但气流逆纤维须丛输运方向流动;当气流吸聚槽始端设置在牵伸钳口前时,在纤维集聚区内的气流流动速度较低,但在自牵伸钳口至气流吸聚槽始端之间的纤维集聚区内,气流顺纤维须丛输运方向流动,而在自气流吸聚槽始端向前的纤维集聚区内,气流逆纤维须丛输运方向流动。     

网格圈集聚纺纱系统三维流场表征与分析

 通过建立流体动力学模型,利用标准κ-ε湍流模型及并行计算技术对网格圈集聚纺纱系统集聚区流场进行了模拟与表征,分析集聚区域内气流的流动状况,解析吸气斜槽入口曲面上气流的静压分布及速度分布规律,并讨论速度分布对须条的作用效果。研究结果表明：网格圈集聚纺纱系统是利用负压效应来产生集聚气流;斜槽入口曲面上的负压使网格圈向异形管内凹;X、Y、Z轴向的速度分量对须条的作用效果各不相同;集聚区产生附加捻度的区域主要靠近吸气斜槽的S1端。     

网格圈集聚纺纱系统三维流场表征与分析

通过建立流体动力学模型,利用标准κ-ε湍流模型及并行计算技术对网格圈集聚纺纱系统集聚区流场进行了模拟与表征,分析集聚区域内气流的流动状况,解析吸气斜槽入口曲面上气流的静压分布及速度分布规律,并讨论速度分布对须条的作用效果。研究结果表明：网格圈集聚纺纱系统是利用负压效应来产生集聚气流;斜槽入口曲面上的负压使网格圈向异形管内凹;X、Y、Z轴向的速度分量对须条的作用效果各不相同;集聚区产生附加捻度的区域主要靠近吸气斜槽的S1端。     

数值分析网孔罗拉气动式紧密纺纱纤维集聚区内的气流流动特征

采用大型流体计算软件模拟网孔罗拉气动式紧密纺纱纤维集聚区内的气流流动状态．并基于数值模拟结果分析了网孔罗拉气动式紧密纺纱纤维集聚区内的气流流动特征、分析认为由于气流吸聚槽自牵伸钳口线位置开始向纤维集聚区左侧倾斜,导致气流吸聚槽左右两侧气流流动方向不同,且气流流动速度差异显著,因此在气流吸聚槽处形成的气流汇聚线更靠近气流吸聚槽的右侧边缘,揭示了网孔罗拉气动式紧密纺纱实践中,被集聚的纤维须丛总是位于靠近气流吸聚槽右侧位置的原因。     

多孔辊筒紧密纺三维流场的数值模拟

通过建立流体动力学模型,对多孔辊筒紧密纺纱系统集聚区流场进行模拟,分析槽宽、内胆负压、导流块对集聚区流场运动的影响。研究表明：多孔辊筒紧密纺纱系统是利用负压效应来产生集聚气流;内胆空气负压小时,抽气管出口速度大;吸风斜槽不同宽度和不同负压对气流集聚产生不同的集聚效果;紧密纺纱装置有导流块比无导流块的集聚效果好。经对比,数值模拟和实验结果得到了比较一致的结论,为气流聚集型纺纱装置的应用提供了可靠的理论依据。     

JWF-A型并条机吸风系统气流流场的数值仿真

为解决JWF-A型并条机吸风系统在生产中存在的问题,采用数值仿真方法分析影响该吸风系统的气流流场、压力场分布和各个吸风口流量大小的因素,并从吸风系统结构参数入手,提出4种改进方案,研究补风口位置与尺寸、风道结构、吸风口开度等对吸风系统流场、压力场和风量大小的影响。仿真计算应用非结构化网格和有限体积法进行计算区域和控制方程的离散,采用标准k-ε模型封闭湍流控制方程。计算结果与实测结果表明：该吸风系统吸风量不足;吸风管道结构不变,补风口位置与尺寸、吸风口开度的变化对系统性能改进作用不大;提出的风道改进方案的吸风量相对于原方案有较大提高,吸风量可以满足要求。     

滚筒内烟丝干燥过程的数值模拟

为了解析滚筒干燥条件对烟丝干燥过程中筒内的温湿度场和流场的影响规律,采用数值模拟开展烟丝滚筒干燥的筒内温湿度场的研究。通过干燥实验测量滚筒内部空气湿度来验证模拟结果的准确性,探究进口热风温度、进口热风速度、筒壁温度和滚筒转速等因素对滚筒干燥过程中内部水分分布的影响规律。结果表明:①增加进口热风温度会使蒸发过程加快;②提高进口热风速度能加强滚筒前段部分的水分蒸发,但进口热风速度过大会造成滚筒内整体水分浓度下降;③改变筒壁温度直接影响烟丝温度与筒内的平衡含水量,筒内平衡含水量随着筒壁温度的升高而增加;④增加滚筒转速会减少烟丝在筒内的停留时间,不利于烟丝的干燥。      

涡流纺纱中纺纱腔内气流结构数值模拟

 利用Fluent软件对涡流纺纱中流场进行了三维动力学模型仿真,研究了进气喷嘴、纺纱腔与空心锭子之间间隙、出口负压强度等参数对纺纱腔内气流结构的影响,并讨论其对纱线特性的影响。研究结果显示：在流量相同情况下,纺纱腔内涡流强度和均匀性与进气喷嘴方向及数量、纺纱腔与空心锭子间隙等相关。进气喷嘴轴线方向越接近纺纱腔横截面方向、纺纱腔与空心锭子间隙越小,涡流强度越大,而进气喷嘴数量越多,涡流形态越均匀稳定;间隙出口负压强度决定纺纱腔内轴向气流速度,该参数由纱线种类及其特性决定。     

不同压强条件下环锭旋流喷嘴内部流场模拟

为探究在不同环锭旋流喷嘴气道入口压强条件下喷嘴内部的流场分布规律,借助STAR-CCM+与ANSYS CFX流体分析软件建立旋流喷嘴模型并进行数值模拟分析,得到在纺纱过程中旋流喷嘴内部气流的速度和压力分布云图。结果表明:空气通入气道入口的流动机制遵循涡流效应,以旋流状向纱道两端流出,向两侧流出的旋流可对纱线进行轻微解捻和毛羽的进一步贴服;喷嘴内部流场对比示意图表明入口压强对纱线受力的分布并无影响,但气流压强波动幅度随入口压强的增大而增大,波动幅度越大越利于毛羽的包裹,对纤维束的包裹作用也更强烈,但过大的气流压强会造成更多纤维的流失。     

Influence of spinning parameters on milkweed/cotton DREF-3 yarn properties

In this study, Pergularia milkweed fibre (70%), cotton fibre (30%) core and 100% cotton fibre sheath DREF-3 core yarns of 74?tex were produced using different spinning parameters in order to understand their effect on yarn properties. Box–Behnken design was used for the optimization of core ratio, drum speed and suction pressure, and to evaluate the effects and interactions of the process variables on the yarn properties at a constant opening roller speed of 12,000?rpm and production speed of 100?m/min. The effects of the core/sheath ratio on all the yarn properties are significant. With an increase in the core/sheath ratio, yarn tenacity and elongation decrease due to insufficient wrapper fibres in the yarn and yarn unevenness; imperfection increases due to higher feed rate and draft at higher core ratio. The yarn hairiness increases at higher core ratio due to higher number of short fibres in milkweed and lesser sheath fibres to cover the core fibres effectively. An increase in the spinning drum speed damages fibre in the sheath and increases the number of hooks at the end of fibres, as a result of which the core yarn tenacity decreases at higher drum speed. At a higher air suction pressure, yarn tenacity and the elongation at break increases. The drum speed and suction pressure have no significant effect on yarn unevenness and imperfections. The yarn hairiness decreases slightly with increase in drum speed and suction pressure but is insignificant.     

回转组合多层筛风道系统仿真分析

利用流体动力学分析软件(FLUENT)对回转组合多层筛风选通道内气流速度、气流方向进行了仿真模拟,得到回转组合多层筛风道系统流道的速度云图。通过观察分析速度云图,发现上沉降室内气流速度不稳定,沉降区速度过大,不能有效沉降轻杂。研究发现上挡风板尺寸及其与进风口的距离直接影响着上沉降室气流速度大小和气流分布状态,经优化后上沉降区域的气流速度明显降低,低速区增大,涡流减少,有效提高了杂质沉降效率和降低能耗。     

Influence of Friction Spinning Process Parameters on Spinnability of Pergularia/Cotton-Blended Yarns

In this study, spinnability of Pergularia daemia seed fiber (70%) and cotton fiber (30%) core/100% cotton fiber sheath DREF-3 core yarns of 74 tex were studied using different spinning parameters in order to understand their effect on yarn properties. Box-Behnken Design was used for the optimization of core ratio, drum speed, and suction pressure and to evaluate the effects and interactions of the process variables on the yarn properties at a constant opening roller speed of 12,000 rpm and delivery rate of 100 m/min. The effect of the core/sheath ratio on yarn quality index is significant. With an increase in the core/sheath ratio, yarn tenacity, and elongation decreases due to insufficient wrapper fibers in the yarn and yarn unevenness increases due to higher feed rate and draft at higher core ratio. An increase in the spinning drum speed increases the yarn quality index up to certain range and then decreases at higher speed due to damaging of fibers in the sheath and more number of hooks at the end of fibers. At a higher air suction pressure, yarn tenacity and the elongation at break increases which ultimately increases the yarn quality index. From the regression analysis, it is observed that the drum speed and suction pressure has no significant effect on yarn unevenness.     

Numerical simulation of flow field in complete condensing spinning: effects of suction unit and guiding device

Complete condensing spinning (CCS) is one kind of pneumatic compact spinning. A kind of hollow roller with strip groove structure on the surface is used to condense the fiber bundle and improve the yarn qualities. In this paper, the numerical simulation of flow field in CCS is studied using fluent software. Using AutoCAD Software, according to the physical parameters of the practical system, a three-dimensional (3D) model of the condensing zone is established firstly. Then, the numerical simulations of the flow field in CCS were presented. Three kinds of suction units, straight-type, long-skewed, and short-skewed, and three kinds of guiding devices, A-type, B-type, and C-type, were discussed. Corresponding simulations in the front, middle, and back condensing zone and arc line along the front roller surface direction were given and analyzed comparatively. It is shown that the flow field distribution in CCS is stable and can condense the fibers well. The shape of suction unit may mainly influence the output of fiber strand in the condensing zone and affect the yarn evenness. When compared with the long-skewed and short-skewed suction units, the straight-type suction unit is beneficial for the fiber strand output leading to better yarn evenness possibly. However, the distribution ranges of flow field in CCS with both long-skewed and short-skewed suction units are larger than that of the straight-type suction unit. Furthermore, comparing with that of without a guiding device, the direct transverse air condensing force in CCS using a guiding device is greatly larger, which is beneficial for reducing the yarn hairiness. However, the assisted condensing forces are smaller and make the yarn evenness possibly worse. Finally, the obtained numerical results are illustrated by spinning experiments.     

禽蛋壳膜回收分选装置参数优化

目的：有效利用废弃蛋壳和蛋壳膜。方法：对废弃蛋壳进行分离和分选,利用Fluent和EDEM耦合仿真研究了分选筒上、下出口直径等结构参数对流场特性、颗粒轨迹的影响,分析了流场特性和壳膜的捕捉率,优化了分选筒的气流出口尺寸。以筒顶角度、吸风机负压、送料口风速和固体负荷率作为试验因素,蛋膜和蛋壳的回收率作为评价指标,进行分选蛋壳膜试验,并进行优化设计。结果：减少分选筒上、下出口直径会增大筒内压降损失和近壁切向速度,当上出口直径为0.4D(D为直筒段直径)、下出口直径为0.5D时,蛋壳和蛋膜的捕捉率最高。筒顶角度为45°,固体负荷率为1 000 g/s,送料口速度为4.64 m/s,吸风机负压为336.61 Pa,此时蛋膜回收率为92.94%,蛋壳回收率为97.90%。结论：上出口负压与进料口风速主要影响分选筒内部流场分布,固体负荷率会使物料之间产生不同的相互作用。在优化后的工艺组合下,该分选设备具有良好的分选效果。     

压力条件对不同尺寸条缝喷嘴换热的影响

以条缝喷嘴型的上下冲击式速冻机内部流场为研究对象,利用计算流体力学(Computational Fluid Dynamics,CFD)数值模拟和实地测试,对比了3种尺寸的喷嘴结构分别在不同压力(190,170,160Pa)条件下3种不同尺寸的喷嘴结构,条件下内部流场及换热特性的区别。结果表明:条缝喷嘴T_0在190Pa条件下的出口风速、努塞尔特数、均匀性比在170Pa条件下的理想,同时横流风速也低。条缝喷嘴T_1在170Pa条件下的出口风速、努塞尔特数、均匀性比在160Pa条件下的理想,但横流风速反而增加。条缝喷嘴T_2与T_0在同一入口压力下相比,只有横流风速较低。在换热强度方面,当入口压力为190Pa时,条缝喷嘴T_1所对应的钢带表面的局部努塞尔特数最大,而T_0与T_1的平均努塞尔特数相差不大。在换热均匀度方面,条缝喷嘴T_0在入口压力为190Pa时的不均匀度最低,换热最均匀。故当空气的质量流量相同时,入口压力为190Pa时所对应的条缝喷嘴T_0能更好地提升换热效率,有利于提升食品的冻结速率。     

气垫式热风箱及纸张传热性能模拟研究

通过最小二乘法研究热空气在气垫式热风箱内的速度、静压、温度分布,探讨了入口风速、高度比、入口温度、开孔率和喷口方式对气垫层不均匀指数、气垫静压和表面传热系数的影响规律。通过量纲分析拟合Nu的函数关系式,数值模拟值与拟合值比较表明,最大相对误差为9.53%,均方根误差为9.5%,拟合方程可为热风箱气垫层表面传热系数的优化研究提供参考。     

Numerical simulation on the condensing effect of suction slot in compact spinning with lattice apron

In this paper, a geometrical model is built by the actual structure of a condensing zone in compact spinning with lattice apron, and a fluid dynamics model is designed by FLUENT to study the numerical simulation of flow field in the condensing zone of straight, oblique, and deformed suction slots. The result shows the laws of airflow static pressure and velocity distribution of three kinds of condensing zones. The difference of distribution between compact direction and adsorption direction of strand is stressed on, which is helpful to make a deeper study on the mechanism of compact spinning with lattice apron and provide a theoretical support for the optimal design of suction slot.