Analysis And Adjustment Of The Airflow Field In The Process Of Cotton Net Lap For The High-efficacy Comber

Cotton comber is the important cotton spinning equipment.With the development of cotton textile industry,the performance requirements of the comber machine are higher and higher,while the airflow in the cotton net lap zone is one of the key factors affecting the velocity of comber.The change of parameters,such as,the negative wind pressure of the tail-suction duct,the comber velocity and the airflow structure of cotton comber's suction noil air duct(the wind scoop and the main air duct),affects the airflow characteristics of the wind tunnel and cotton net lap zone,thus impacting the normal lap of cotton net.In this paper,the three-dimensional model of cotton comber's suction noil air duct was established to study the dynamic performance of the airflow field in cotton comber,and the deformation pattern of cotton whisker under the action of airflow in the process of cotton net lap was simulated,which was verified by the test.(1)First of all,in order to explore the distribution of the airflow field in the interface between the wind scoop with the main air duct(that is,the “eight eyes suction mouth”)and make the wind volume of the “eight eyes suction mouth” nearly uniform,the airflow field of the main air duct in cotton comber was performed on the asis of computational fluid dynamics,and the structure change of the main air duct on the influence of airflow field distribution was studied.The simulation results show that the wind speed,the wind pressure and the wind volume of each eye wind mouth are not uniform when the “eight eyes suction mouth” are all the same size.The closer to the tail-suction,the larger the wind velocity and wind volume,and the smaller the wind pressure.Therefore,in order to make the wind volume of the “eight eyes suction mouth” consistent,it must be realized by adjustment or field test.Therefore,by changing the area size of each "eight eyes suction mouth" or the cross-sectional area of the main duct of the comber,the wind volume of the "eight eyes suction mouth " is approximately uniform.In addition,when the cross-sectional area of the main duct of the comber is constant,if the square structure of the main duct is changed to a circular structure,a single vortex formed along the circular section flows more smoothly in the tube.This can effectively reduce the pressure energy loss caused by the formation of multiple vortices along the square section of the original square main duct.(2)In order to study the distribution of the airflow field in the actual working condition,the airflow field of the three-dimensional model of comber's suction noil air duct and the cylinder,the clamp plate and brush of the movement boundary were dynamically simulated through the dynamic mesh technology.The influence of the negative wind pressure of the tail-suction duct,the comber velocity and the airflow structure of cotton comber's suction noil air duct on the airflow field were investigated,and the wind speed and wind pressure test were carried out for the “eight eyes suction mouth”.The results show that the airflow is sucked in the air inlet,flows to the main duct centrally,forms the converging flow at the interface between the main duct and the wind scoop,and flows out with multiple vortex.The closer to the tail-suction,the higher wind velocity,and the smaller the wind pressure in main air duct.The high-speed rotation of cylinder and brush forms the attached laminar airflow which is high speed in the narrow airflow passage,leading to the generation of vortices and the gradient distribution of wind speed and wind pressure.At the beginning of the cotton net lap,the airflow channel between the cylinder and the rear separation roller is opened momentarily,and the newly combing cotton is pressed down under the airflow and then quickly overlaps with the cotton net introduced by the roller.The transient “closure” is formed quickly between the cylinder and the triangle airflow plate and brush,resulting that the wind speed is slowly increasing,and the wind pressure is slowly decreasing in a relatively low velocity.The dynamic airflow is relatively stable which makes the overlapped cotton net smoothly forward and is held by the rear separation roller and the leather roller.At this time,the cotton net inserts the top comb for “combing”,and the airflow channel is open between the cylinder groove part and the brush,and the dropped cotton and impurities are sucked out through the wind scoop and the main air duct.Cotton comber works in negative pressure.The wind speed is increasing,while the wind pressure is decreasing from the wind scoop to the main air duct.The wind pressure decreases with the increase of wind speed.The simulation data of airflow field of the “eight eyes suction mouth” is consistent with test result,which shows that the simulation model and simulation method are correct and effective.Based on the research above,with the increase of the negative wind pressure in the tail-suction,the wind speed and negative wind pressure have an increasing trend in the cotton net lap zone.Furthermore,with the increase of the comber velocity,the wind speed and negative wind pressure show the increasing trend in the cotton net lap zone,then the airflow is turbulent state,while there's the blockage and anti-surge phenomenon when the transient “closure” is formed quickly between the cylinder and the triangle airflow plate and brush.Therefore,through adjusting the airflow structure of the high-speed comber,the vortex is reduced and the airflow is smooth,while the airflow field is relatively stable when the cotton net is overlapped.(3)The single coupling model between the airflow field in cotton comber's suction noil air duct and equivalent cotton whisker was established,and the airflow field during the movement of cotton whisker was simulated in the process of otton net lap.The airflow data obtained from the simulation was loaded on the surface of the equivalent cotton whisker,then the nonlinear static force of cotton whisker under wind pressure was analyzed,and the deformation pattern of the cotton whisker with time was match with the actual image of high-speed photography.