Study On Condensing Principle And Yarn Properties Of Compact Spinning With Perforated Drum

Because of the existing of spinning triangular space, traditional ring spun yarns have a lot of hairiness. The quality of yarns is impacted seriously, and cannot meet the ever-increasing needs of people’s material and culture life. The appearance of compact spinning technique has successfully solved the problem of yarn hairiness. Compact spinning is a technique based on traditional ring spinning system, in which a condensing zone is added between front roller and yarn formation zone. The loose yarn bundle outputted from front roller is condensed by compact device, and then spinning triangular decreases, yarn hairiness reduces, yarn structure compacts, and yarn strength increases.Taking compact spinning with perforated drum as research object, velocity distribution of airflow field and motion of fibers in condensing zone are simulated, and then condensing principle of the fiber bundle is obtained. The simulation results are verified by yarn properties testing and comparing with traditional ring spun yarn under the same condition.Firstly, Computational fluid dynamics (CFD) software—Fluent is used to simulate the velocity distribution of airflow field in condensing zone of compact spinning system with perforated drum. And then velocity distribution of airflow field in different fibrous layers under a particular negative pressure can be obtained, so it is with velocity distribution in the same position under different negative pressure. The results indicate that there is a positive correlation between velocity of airflow field and the height of fibrous layers over perforated drum under a particular negative pressure, and velocity of airflow field in the same position becomes larger with the increase of negative pressure under different negative pressures.Secondly, MatLab software is used to simulate trajectory of the fibers and condensing principle of the fiber bundle in condensing zone, and then the relationship among negative pressure, skin fraction coefficient of perforated drum and condensing effect is discussed. The results indicate that the condensing process can be divided into three different phase, that is, fast convergence phase, adjusting convergence phase, convergence completion phase. There is a negative correlation between skin fraction coefficients of perforated drum and condensing effect of fiber bundle under a particular negative pressure, that is, there exists a critical skin fraction coefficient, which can guarantee the fiber bundle convergence better. The skin fraction coefficient of perforated drum becomes larger with the increase of negative pressure under variable negative pressure. In theory, the fiber bundle can condense under a lower negative pressure if the critical skin fraction coefficient is small enough, so energy consumption will decrease in this condition, while this will increase the cost of production at the same time. Therefore, it is very important to choose a reasonable negative pressure and skin fraction coefficient of perforated drum to balance energy consumption and cost of production in the practical production. It can provide a theoretical direction to obtain "lower energy consumption, lower cost of production, and higher yarn quality" compact spinning yarn.Finally, particular negative pressure and skin fraction coefficient of perforated drum are chosen, compact spinning yarn with perforated drum and traditional ring spinning yarn are spun with the same yarn count and twist number under the same fore-spinning process. The comparison of yarn structures and properties spun by these two systems indicate that compact spinning yarn with perforated drum has much larger volume density, tighter structure, clearer twisting spiral structure, smoother appearance, and less hairiness. Because of these properties for compact spinning yarn, it has higher breaking strength, abrasion resistance and bending stiffness.On the whole, simulation of airflow field in condensing zone of compact spinning system with perforated drum makes the velocity distribution of airflow field visualize; simulation of condensing effect makes the macro-objective microscopic; from the comparison of yarn properties, impact of airflow to yarn properties can be obtained. It can provide an important theoretical direction to the transform of compact spinning system with perforated drum.