Study On Yarn Forming Mechanism And Property Of Lateral Compact Spinning With Suction Groove

In the hundred years since its birth,ring spinning is still occupying a dominant position in the spinning industry,because of its own advantages in drafting,twisting and winding principles.One of the biggest problems in ring spinning is the twisting triangle.In order to solve this problem,many new ring spinning technologies have been developed based on the ring spinning itself,one of which is compact spinning.Compact spinning machines are improved on the original ring spinning frame which mainly aiming at the problem of yarn hairiness caused by the twisting triangle of ring spinning.The principle of compact spinning is to minimize the width of the drafted strands before twisting into yarn and complete the addition of twists in the process,and finally achieve the goal of reducing the hairiness of yarn.Several popular spinning systems in compact spinning,such as the compact spinning system with lattice apron,compact spinning with perforated drum system and punched apron compact spinning system,are all equipped with a compact device before the front roller,or adding an output roller after the compact device.Due to these structures of the device,when the fiber strands are gathered,they will be held by the rollers,resulting in the destruction of the strand structure after the completion of gathering and affecting the gathering results.Ultimately affects the hairiness of the yarns,which cannot reflect the advantages of compact spinning.And these compact spinning methods mainly used in cotton and cotton type fiber spinning.For wool,ramie and other natural fiber with long length and large length dispersion,the agglomeration effect of this kind of equipment is limited due to its agglomeration principle,and the improvement effect of yarn hairiness is very limited,which affects the final yarn structure and performance.Agglomeration spinning products occupy a dominant position in the market of high-grade cotton fabrics,while traditional long-spun products such as wool and ramie have to go through singeing process to achieve smoothness of fabrics.Singeing process will not only have a great negative impact on the environment,but also increase the processing load,reduce the utilization of fiber raw materials and increase the cost burden of textile enterprises.Therefore,high-grade fabric market for compact spinning products made by wool,ramie and other long fiber products demand will also continue to rise.Over the past decade,the long-fiber compact spinning technology has also been developed.This paper mainly researches the compact spinning of suction groove technology and improves the device on this basis.And putting forward a new spinning method which is called lateral compact spinning with suction groove,conducting theoretical research and experiments on it.Finally,to find a convenient and high-quality method of spinning natural long fibers such as wool and ramie.In this paper,improvements are made on the basis of the compact spinning with suction groove,and lateral compact spinning with suction groove is proposed.In addition,systematic research has been carried out on the concentrated spinning method of lateral compact spinning with suction groove.Firstly,the airflow groove collector roller is optimized,and the agglomeration area formed by the front roller,the sideentrance airflow groove collector roller,the front rubber roller and the spinning tube is delineated,and a three-dimensional calculation model of the fluid flow in the agglomeration area is established.The Fluent software is based on the principle of CFD.Perform simulation calculations to analyze the airflow static pressure and velocity distribution in the accumulation area.Then,using the finite element method to establish a fiber model to simulate the movement trajectory of the fiber in the condensing area of the lateral compact spinning with suction groove.After that the additional twists in the condensing zone and the transmission of the twist resistance are analyzed.Finally,through mathematical analysis and combined with airflow theory,the end breakage in spinning is analyzed and tested and based on the previous theory,comparative ramie yarn experiments were carried out to analyze the yarn-forming properties of the lateral compact spinning with suction groove.The main research contents and conclusions of this article are as follows:(1)The principle and structure of the lateral compact spinning with suction groove spinning device is rebuilt.The structure of the air suction bladder and flute are improved.Based on this,lateral compact spinning with suction groove roller is designed.Through the three-dimensional flow in the lateral compact spinning with suction groove spinning device: the front roller,the front rubber roller and the suction groove area,establishing its three-dimensional fluid dynamics model.Analyze the static pressure distribution and velocity distribution law of the air flow in the flow field by the Ansys16.0 software simulation results.(2)The air distribution in the agglomeration area is analyzed.The whole agglomeration area is divided into pre-agglomeration area and main agglomeration area.In the pre-agglomeration area,the influence of the variation of air flow on the spacing between the lateral compact spinning with suction groove and the front rubber roller is analyzed.The results show that when the spacing is 0.5 mm,the air in the preagglomeration area will generate turbulence,which is unfavorable to the fiber movement and will increase the end breakage rate in the pre-agglomeration area in the spinning process.In the main agglomeration area,the distributive law of the flow field in the accumulation area under different groove shapes,different hole sizes and different negative pressures are compared.Comparing the collection devices with different groove shapes,it is shown that the air flow in the single side of the asymmetric groove(lateral compact spinning with suction groove)is larger than that of the symmetric collection groove.The speed is also greater than that of symmetrical grooves.Comparing the influence of different negative pressures on the accumulation speed when adopting the lateral compact spinning with suction groove device,the result is that the accumulation speed with a large negative pressure is relatively large,which is conducive to fiber accumulation to a certain extent.The symmetrical grooves are used to simulate the distribution of small pores with different hole sizes.The results show that the large hole size has a higher flow velocity in the direction of aggregation,which is more conducive to fiber aggregation.(3)In this paper,the finite element method is adopted to establish the elastic thin rod fiber model to simulate the movement trajectory of the fiber in the agglomeration area.The fiber model uses a dynamic method to analyze the large deformation of the fiber in space,which makes the calculation simple,and the shape of the simulated fiber in the aggregation area is closer to the real fiber movement.Through two the air velocity distribution data obtained by flow field simulation,the motion state of single fiber under the joint action of air flow and groove is simulated,and the motion of fiber strand under the action of groove is simulated by this model,too.The results show that in the single fiber trajectory simulation,when the fibers gather under a large air velocity,the agglomeration point is closer to the front roller,which indicating that large negative pressure can accelerate the agglomeration of fibers.The simulation results of fiber strand show that when the fed position of fiber strand is the lateral the side of the compact groove,the fiber strand will roll along the groove roller to form an additional twist.And the additional twists will be transmitted to the front roller,which can reduce the floating area of the pre-agglomeration area and reduce the spinning breakage in the pre-agglomeration area.(4)The twist transmission in the agglomeration area is analyzed.The principle of lateral compact spinning with suction groove determines that the lateral compact spinning with suction groove roller integrates gathering and twist resistance.By analyzing the twist resistance moment of the accumulation zone,the twist resistance model of the accumulation zone is established.By analyzing the transfer of additional twist in the accumulation zone and the twisting torque and twist-resisting torque during spinning,the additional twist model and the twist-resisting model of the accumulation zone are established respectively.The study of additional twist transmission can conclude that the additional twist transmission length,the angle of the roller groove of the lateral compact spinning with suction groove,the friction coefficient of the groove,the radius of the fiber strands,and the radius of the roller of the lateral compact spinning with suction groove can affect the transmission of additional twist.The research results on the influence factors of the twist blocking effect can conclude fiber strands are gathered and twisted in the gathering area,and the twist resistance point of the fiber strands in the gathering area generally does not break through the gathering area.The anti-twist effect increases with the increase of the spinning tension,negative pressure,the diameter of the gathering suction hole and the friction factor between the gathering groove of the lateral compact spinning with suction groove roller.At the complete agglomeration point,the above-mentioned factors that affect the twist resistance must be reasonably configured,otherwise the twisting will be carried out when the strands have not yet been gathered,and the gathering effect of the strands will be compromised.(5)Finally,the causes of yarn breakage are comprehensively analyzed,and the spinning experiment of long spinning fiber is carried out.Through the analysis,it is concluded that the smaller the spacing between the lateral compact spinning groove roller and the front rubber roller,the smaller the length of the floating area.The comprehensive theoretical analysis shows that the spinning breakage should be the smallest when this spacing is 1mm.The breakage theory is verified by wool and ramie fiber spinning,and the experimental results are in line with the theoretical analysis.In the end breaking experiment,the experiment of changing the feeding direction is designed.The experiment results show that the laterally fed yarn can also reduce end breaking in the floating area during the yarn forming process due to the existence of additional twist.This paper designed a certain amount of the experimental plan by using the lateral compact spinning with suction groove device spin different specifications of ramie yarn.The ramie yarns with different feeding positions,negative pressure and air suction aperture and different spinning tension were compared,the longitudinal microstructure of the yarn was observed,and the properties of hairiness,strength and twist were tested and compared.The conclusion is that the yarn forming performance of lateral compact spinning with suction groove is better than that of symmetrical groove compact spinning.Because the asymmetrical shape of groove changes the distribution of airflow in the gathering area and improves the utilization rate of airflow,the yarn hairiness is reduced and the strength is improved.The influence of negative pressure on spinning is that spinning yarn with a certain fineness,when increasing the negative pressure within a certain range is conducive to the reduction of harmful hairiness above 4mm.However,when the spinning fineness is16.7 tex and the negative pressure is 3400 Pa,due to the reduction of the number of fibers in the yarn section and the high initial modulus of ramie fiber dimension,the fibers in the yarn body are easy to be sucked into the air suction device.The hairiness is reduced;however,it causes fiber loss and strength reduction.In different hole suction,lateral compact spinning with suction groove device with different aperture circles arranged regularly has better spinning effect.The different effects of ramie long fiber spinning carried out by this device provide a theoretical and practical basis for the application of the agglomeration spinning device in long fiber spinning in the future.