Xinjin Liu

Research on pneumatic compact spun yarn quality

Compact spinning is one of the most important improvements of traditional ring spinning, which is implemented by adding a fiber condensing device to condense the fiber bundle and decrease the spinning triangle. Pneumatic compact spinning is the most widely used compact spinning method at present. Compact spinning with perforated drum and compact spinning with lattice apron are the two main kinds of pneumatic compact spinning. Therefore, in this paper, comparison analysis of yarn quality between compact spinning with perforated drum and compact spinning with lattice apron is presented. First, 9.7 tex cotton-combed yarn is spun in three different kinds of pneumatic compact spinning systems, including two kinds of compact spinning with perforated drum: Rieter’s COM4 and complete condensing spinning system (CCSS), and one lattice apron compact spinning system: Toyota’s four-line compact spinning. The test results of yarn qualities show that comparing with other two kinds of compact spinning systems, the yarn ...Compact spinning is one of the most important improvements of traditional ring spinning, which is implemented by adding a fiber condensing device to condense the fiber bundle and decrease the spinning triangle. Pneumatic compact spinning is the most widely used compact spinning method at present. Compact spinning with perforated drum and compact spinning with lattice apron are the two main kinds of pneumatic compact spinning. Therefore, in this paper, comparison analysis of yarn quality between compact spinning with perforated drum and compact spinning with lattice apron is presented. First, 9.7 tex cotton-combed yarn is spun in three different kinds of pneumatic compact spinning systems, including two kinds of compact spinning with perforated drum: Rieter’s COM4 and complete condensing spinning system (CCSS), and one lattice apron compact spinning system: Toyota’s four-line compact spinning. The test results of yarn qualities show that comparing with other two kinds of compact spinning systems, the yarn spun in CCSS has the best evenness, least long hairiness, and slightly lower strength. Then, the properties of spun yarns are analyzed using two methods. First, using Fluent Software, numerical simulations of three-dimensional flow field in condensing zone of three kinds of compact spinning system are presented, respectively. Second, the fiber movements in condensing zones are captured using high speed camera system OLYMPUS i-speed3.

Research on spun yarn qualities in a modified ring-spinning system using airflow-twisting device

In this paper, a kind of airflow-twisting devices which can produce the twist by the high vortex airflow is employed for improving the twist propagation process of ring-spinning system. Firstly, three different kinds of yarns Ne20, Ne40, and Ne60 are spun in this modified ring-spinning system with five different airflow pressures and two different swirling directions, including anticlockwise and clockwise, and the qualities of spun yarns, including hairiness, strength, evenness, and number of snarling characterizing the yarn residual torque, are measured. Secondly, the images of spinning triangles are captured by using a high speed camera system OLYMPUS i-speed3, and the mechanism of the effects of vortex airflow on yarn qualities is discussed by analyzing the fiber tension distributions in the spinning triangle. It is shown that for the ‘Z’ twist spun yarn, the spinning triangle decreases with the increasing of clockwise airflow pressures, whereas the triangle becomes more and more symmetrical with the increasing of anticlockwise airflow pressures. Meanwhile, the comprehensive qualities of spun yarn are improved with the increasing of both directions of airflow pressures to a certain extent. However, the hairiness and strength of spun yarn will be mainly improved with clockwise airflow, whereas yarn residual torque mainly reduced with anticlockwise airflow.In this paper, a kind of airflow-twisting devices which can produce the twist by the high vortex airflow is employed for improving the twist propagation process of ring-spinning system. Firstly, three different kinds of yarns Ne20, Ne40, and Ne60 are spun in this modified ring-spinning system with five different airflow pressures and two different swirling directions, including anticlockwise and clockwise, and the qualities of spun yarns, including hairiness, strength, evenness, and number of snarling characterizing the yarn residual torque, are measured. Secondly, the images of spinning triangles are captured by using a high speed camera system OLYMPUS i-speed3, and the mechanism of the effects of vortex airflow on yarn qualities is discussed by analyzing the fiber tension distributions in the spinning triangle. It is shown that for the ‘Z’ twist spun yarn, the spinning triangle decreases with the increasing of clockwise airflow pressures, whereas the triangle becomes more and more symmetrical with the i...

Research on fiber tension at asymmetric spinning triangle using the finite-element method

Spinning triangle is a critical zone in the ring spinning process of staple yarn, whose geometry influences the fiber tension distribution in the spinning triangle directly and determines the spun yarn qualities. In ring spinning, the spinning triangle is often asymmetric due to the inclination angle of the spinning tension or the migration of the axis fiber at the front roller nip. Therefore, in this paper, the fiber tension distributions in the asymmetric spinning triangle due to the migration of the axis fiber at the front roller nip were studied using the finite element method (FEM). In the direct finite-element model, the initial strain of the axis fiber is set as zero, and the accidental fiber tensions would be produced due to the asymmetric distributions of the initial strain on fibers in the two sides of the spinning triangle. Then, an effective finite-element model of the asymmetric spinning triangle with right (left) axis fiber migration for calculating the fiber tension is built by composing an...Spinning triangle is a critical zone in the ring spinning process of staple yarn, whose geometry influences the fiber tension distribution in the spinning triangle directly and determines the spun yarn qualities. In ring spinning, the spinning triangle is often asymmetric due to the inclination angle of the spinning tension or the migration of the axis fiber at the front roller nip. Therefore, in this paper, the fiber tension distributions in the asymmetric spinning triangle due to the migration of the axis fiber at the front roller nip were studied using the finite element method (FEM). In the direct finite-element model, the initial strain of the axis fiber is set as zero, and the accidental fiber tensions would be produced due to the asymmetric distributions of the initial strain on fibers in the two sides of the spinning triangle. Then, an effective finite-element model of the asymmetric spinning triangle with right (left) axis fiber migration for calculating the fiber tension is built by composing an asymmetric spinning triangle with a corresponding left (right) axis fiber migration and a symmetric spinning triangle is composed. Then, the fiber tension distributions in the spinning triangles in the Ne40 (14.6 tex) and Ne60 (9.7 tex) cotton spun yarn were numerically simulated with different axis fiber migrations and twist factors. Furthermore, the accuracy of the proposed finite-element model in calculating the fiber tension distribution in the asymmetric spinning triangle was validated by comparing it with the theoretical model built by the energy approach. It is shown that the numerical values of fiber tension distribution between the FEM results and the results with the energy method are in good agreement. Meanwhile, with the increase in the migrations of the axis fiber or the yarn twist, fiber tension in the spinning triangle is increased.

The acoustic characteristics of dual-layered porous nonwovens: a theoretical and experimental analysis

The normal incidence sound absorption coefficient of single-layered porous materials predicted using some prediction models is well known. The published acoustic behaviors prediction models, such as Biot model, Zwikker and Kosten model, Delany and Bazley model, and Champoux and Allard model, can give acceptable prediction results by only taking specific flow resistivity and material thickness as independent variables to estimate the normal incidence sound absorption coefficient. However, the existing literature fails to provide proper knowledge regarding the acoustic characteristics of dual-layered porous nonwoven absorbers. So, the aim of this paper was to propose a theoretical acoustic model for dual-layered porous nonwoven absorber and to verify the proposed model experimentally. In theory aspect, the study focused on the extension algorithm of the Zwikker and Kosten model for dual-layered nonwoven absorber. The theoretical analysis of the impact of thickness and porosity of outer and inner layer on sound absorption coefficient was detailed using numerical simulation method. In experiment aspect, we particularly designed 20 dual-layered nonwoven absorbers with four types of meltblown polypropylene nonwoven materials and five types of hydroentangled E-glass fiber nonwoven materials firstly. Secondly, the calculated sound absorption coefficients using the proposed model were compared with the measured ones of the 20 dual-layered nonwoven absorbers at 250, 500, 1000, and 2000 Hz. Experimental results indicate that the measured and the calculated data have very similar trend with the change of thickness, porosity, and the sound frequency, apart from the obvious difference between them at low frequency.

Theoretical study of spinning triangle with fiber concentric circular cones arrangement at front nip line

Spinning triangle is a critical region in the spinning process of staple yarn, which geometry influences the mechanical performances of fibers in the spinning triangle and determines the physical performance of spun yarns directly. Taking appropriate measures to reduce the spinning triangle and improve the qualities of yarn has attracted great interesting recently. In these modified ring spinning systems, the fibers in the spinning triangle are not arranged in the same plane, but arranged in concentric circular cones at front nip line, such as compact spinning, in which a fiber-converging device is installed on ring spinning frame, and the fiber bundle can be condensed before twisting in order to reduce the spinning triangle. Therefore, in this paper, a new theoretical model of fiber tension distribution in the spinning triangle with fiber concentric circular cones arrangement at front nip line is proposed based on the principle of minimum potential energy firstly. Then, corresponding residual torque within a yarn caused by the fiber tension is given. Finally, as an application of the proposed method, taking the spinning triangle in Ne40 cotton yarn 3-line rollers compact spinning as an example, the fiber tension distributions in the spinning triangle both with and without fiber buckling and corresponding residual torque within a yarn are numerically simulated, and the results are compared with those from earlier model. Furthermore, the properties of spun yarns produced by compact spinning system and ring spinning system are evaluated and analyzed.

Research on mechanical properties of fibers at asymmetric ring spinning triangle using Finite Element Method

In the ring spinning process of staple yarn, spinning triangle is a critical zone, whose geometry influences the mechanical properties of fiber in the spinning triangle directly. In the practical spinning, especially in some modified ring spinning systems, the spinning triangle is often asymmetric, in which the horizontal deviation of the twisting point is existed and lead to an obvious angle between the yarn spinning tension and the vertical axis perpendicular to the nip line. Therefore, in this paper, the fiber tension distributions in this kind of asymmetric spinning triangle were studied using the finite element method. In the direct finite element model, the initial strain of fibers in the two sides of spinning triangle is asymmetric, and corresponding accidental fiber tensions would be produced, which makes the fiber move to the middle of the spinning triangle and lead to inaccurate results. Therefore, in the paper, one new finite element model of the asymmetric spinning triangle with left (right) h...In the ring spinning process of staple yarn, spinning triangle is a critical zone, whose geometry influences the mechanical properties of fiber in the spinning triangle directly. In the practical spinning, especially in some modified ring spinning systems, the spinning triangle is often asymmetric, in which the horizontal deviation of the twisting point is existed and lead to an obvious angle between the yarn spinning tension and the vertical axis perpendicular to the nip line. Therefore, in this paper, the fiber tension distributions in this kind of asymmetric spinning triangle were studied using the finite element method. In the direct finite element model, the initial strain of fibers in the two sides of spinning triangle is asymmetric, and corresponding accidental fiber tensions would be produced, which makes the fiber move to the middle of the spinning triangle and lead to inaccurate results. Therefore, in the paper, one new finite element model of the asymmetric spinning triangle with left (right) horizontal deviation was presented for calculating the fiber tension. In the model, an asymmetric spinning triangle with the same right (left) horizontal deviation was used to combine with the original asymmetric spinning triangle, and one axisymmetric quadrangle was built, and the symmetry axis is the central fiber. Then, the fiber tension and torque distributions in the spinning triangles of Ne40 (14.6 tex) and Ne60 (9.7 tex) cotton spun yarn were numerical simulated with different horizontal deviations and twist factors. Furthermore, the accuracy of the proposed finite element model in calculating the fiber tensions was validated by comparing it with the theoretical model built by the energy approach.

Research on evenness of section-color yarn

Section-color yarn is a kind of fancy yarn, which has discontinuous color changing on yarn axial direction and meets the needs of the market. Therefore, it is of high added value. In the section-color yarn spinning, one white roving is feeding into the back roller continuously, and one color roving is feeding into the middle roller discontinuously, and corresponding discontinuous color change on yarn axial direction can be produced. Compared to the common ring spun yarn, the evenness of section-color yarn is worsening seriously due to its spinning mechanism. Therefore, in this paper, the evenness of section-color yarn is analyzed. It is shown that the feeding deviation of color roving is the main possible reason for the worsening evenness of section-color yarn. Then, the corresponding measure for improving section-color yarn evenness is taken by modifying the feeding time of the back roller, and the corresponding modified spun yarn evenness is measured. It is shown that the section-color yarn evenness can...Section-color yarn is a kind of fancy yarn, which has discontinuous color changing on yarn axial direction and meets the needs of the market. Therefore, it is of high added value. In the section-color yarn spinning, one white roving is feeding into the back roller continuously, and one color roving is feeding into the middle roller discontinuously, and corresponding discontinuous color change on yarn axial direction can be produced. Compared to the common ring spun yarn, the evenness of section-color yarn is worsening seriously due to its spinning mechanism. Therefore, in this paper, the evenness of section-color yarn is analyzed. It is shown that the feeding deviation of color roving is the main possible reason for the worsening evenness of section-color yarn. Then, the corresponding measure for improving section-color yarn evenness is taken by modifying the feeding time of the back roller, and the corresponding modified spun yarn evenness is measured. It is shown that the section-color yarn evenness can be improved effectively, and the maximal improvement rate is 13.19%, which proves the effectiveness of the given method in this paper.

Effects of lattice apron density on yarn qualities in Four-line compact spinning system

In the paper, using finite element method (FEM), the effects of lattice apron density on yarn qualities in Four-line compact spinning system were studied by analyzing the numerical simulations of the airflow velocity. Firstly, three different kinds of yarns, 18.2tex (32S), 9.7tex (60S), and 5.8tex (100S), were spun on FA507B spinning frame equipped with lattice aprons of mesh size 150, 120, and 100, respectively. The hairiness, breaking strength, and evenness of spun yarns were tested and comparatively analyzed. Secondly, using FEM, the numerical simulations of the airflow velocity in the condensing zone were presented. The finite element model of condensing zone was constructed according to the physical parameters of the practical system. Then, the simulation of airflow velocities on five straight lines located in the front, middle, and back of condensing zone were given. It is shown that, in the whole condensing zone, for the lattice apron with mesh size 100, the direct transverse condensing force is high, but the assisted condensing force is low and disorder, which is not beneficial for yarn qualities. Compared to the lattice apron with mesh size 150, the usage of lattice apron with mesh size 120 may be beneficial for the high-count yarn condensing or the yarn condensing under the relatively lower negative pressures. Furthermore, taking the 9.7tex as an example, the trajectory of yarn movement in the condensing zone was given using high-speed camera system OLYMPUS i-speed3. Corresponding airflow velocities along the yarn movement path were presented.In the paper, using finite element method (FEM), the effects of lattice apron density on yarn qualities in Four-line compact spinning system were studied by analyzing the numerical simulations of the airflow velocity. Firstly, three different kinds of yarns, 18.2tex (32S), 9.7tex (60S), and 5.8tex (100S), were spun on FA507B spinning frame equipped with lattice aprons of mesh size 150, 120, and 100, respectively. The hairiness, breaking strength, and evenness of spun yarns were tested and comparatively analyzed. Secondly, using FEM, the numerical simulations of the airflow velocity in the condensing zone were presented. The finite element model of condensing zone was constructed according to the physical parameters of the practical system. Then, the simulation of airflow velocities on five straight lines located in the front, middle, and back of condensing zone were given. It is shown that, in the whole condensing zone, for the lattice apron with mesh size 100, the direct transverse condensing force is hi...

Research on flow field in a modified ring spinning system with the air nozzle

Abstract Twisting is one of the most important steps in the yarn spinning, which influences the geometry of spinning triangle and determines the properties of spun yarns. Airflow is one of the most important measures on improving yarn spinning. In this paper, a kind of air nozzle with vortex guiding channel was designed and used on the modification of ring spinning system, and the spun yarn qualities was studied by analyzing the airflow field in the nozzle. Firstly, the three-dimensional physical model of nozzle was given using CAD software according to the geometrical size of the practical nozzle model. Then, the numerical simulations of the three-dimensional flow field in the nozzle were given using Fluent software. Finally, two different kinds of yarns 10Ne and 20Ne were spun in the modified ring spinning system with the nozzle installed. The airflow pressure 0.01 Mpa and two different swirling directions, anticlockwise and clockwise, were chosen. The qualities of spun yarns, hairiness, strength, evenness, and number of snarling were measured and analyzed. It is shown that the high vortex airflow can be produced in the nozzle, and then corresponding twist can be produced. For the Z(S) twisting spun yarn, under the effects of the clockwise (anticlockwise) vortex airflow, the pre-twisting would be produced and the yarn twist can be strengthened, while under the effects of the anticlockwise (clockwise) vortex airflow, the untwisting effect would be produced, and the yarn twist can be decreased.

Research on fiber distribution in front draft zone of super high draft ring spinning based on cut-middles method

Abstract A super draft ring spinning machine was designed to spin high-count cotton yarns. It was equipped with four-line draft system (FLDS) and four aprons. For yarns spun on FLDS, it often occurs that yarn unevenness increased compared with three-line draft system (TLDS). In the paper, by cut-middles method, the fiber distribution in front draft zone of FLDS draft system was studied, and corresponding yarn qualities were analyzed. First, comparison analysis of yarn quality between FLDS and TLDS was presented. Cotton yarns of 9.7 and 7.3 tex were spun by TLDS and FLDS ring spinning machine, respectively. The results shows that for 9.7 tex cotton yarn, slower fibers in yarns spun on FLDS are more than that in yarns spun on TLDS. For FLDS, the friction field at the back of front draft zone is stronger, which improves yarn evenness. However, for 7.3 tex cotton yarn, accelerated point of fibers on FLDS is nearer to nipper bite of front roller than that on TLDS. Thus, evenness of yarns spun on FLDS is better. Then, 4.9 tex cotton yarn was taken as an example, and they were spun by four kinds of draft distributions on FLDS. The results indicate that for 4.9 tex cotton yarns spun by 64.1 × 1.60 × 1.15, slower fibers at the back of front draft zone are mostly found. And accelerated point of fibers is nearest to nipper bite of front roller. Therefore, 4.9 tex cotton yarns spun by 64.1 × 1.60 × 1.15 have best yarn evenness.