Study Of Airflow Characteristics During Rotor Spun Composite Yarn Spinning Process And Yarn Parameter Optimization

Rotor spinning is also known as air spinning. Based on the interaction of the airflow and high speed rotor, fibers are transmitted, condensed and twisted, finally become yarns by guide roller. Many studies on the spinning mechanism, spinning technology and yarn properties of rotor spinning are researched by scholars both in China and abroad. However, there are few researches about the rotor spinning composite yarn. And no paper about the characteristics of airflow in the rotor spinning composite yarn is published. Thus, the spinning channel of rotor spinning composite yarns was the research subject. The airflow field in the spinning channel was calculated based on the Fluent software. The impacts of the spinning processing parameters on cotton polyurethane rotor spinning composite yarn and cotton polyester rotor spinning composite yarn were explored. Then, the spinning processes of two types of composite yarns were optimized based on orthogonal test to obtain the optimum process parameters for two types of composite yarns respectively.The numerical simulation method of the governing equations and turbulence of the fluid flows were introduced. The geometrical model of the flow field in the spinning channel is established. The meshing and the boundary conditions were set. The influence of groove model, rotor diameter and rotor speed on the airflow in the rotor were analyzed. The results show that the least pressure of guide tube is-9810.61 Pa. The pressure at the inlet of transport channel is positive pressure. The pressure at the outlet is negative pressure. The pressure in the rotor is between-9810.61 Pa and 4518.77 Pa. The velocity in the guide tube is 164.82 m/s and 219.76 m/s. The airflow speeds up in the gradually shrinking transport channel. And the speed increases to 384.58 m/s at the outlet of the channel. Then the airflow enters the rotor. When the airflow reaches the intersection of the transport channel and the rotor slip plane, it separates into two currents of opposite direction airflow. Under the same process conditions, when the rotor speed was 120000 r/min and the diameter of the rotor is 36 mm, the pressure in the groove is T>S>G>U, the velocity is U>G>S>T. When the rotor speed was 120000 r/min and the diameter of the rotor is 42 mm, the pressure in the groove is U>S>T, the velocity is T>S>U. When the rotor speed was 120000 r/min and the diameter of the rotor is 46 mm, the pressure in the groove is U>V>T, the velocity is T>V>U. When the rotor speed was 120000 r/min and the groove is T type, the pressure in the groove of different diameters is T₄6>T₄2>T₃6, the velocity is T₃6>T₄2>T₄6. When the rotor speed was 120000 r/min and the groove is U type, the pressure in the groove of different diameters is U46>U42>U36, the velocity is U36>U42>U46. When the groove is T type and the diameter of the rotor is 46 mm, at the range from 0o to 250o and from 290o to 360o in groove, the pressure in the groove of different speeds is T₄>T₁₂>T₂0, the velocity is T₂0>T₁₂>T₄. When the groove is T type and the diameter of the rotor is 46 mm, at the range from 0o to 360o in groove, the pressure in the groove of different speeds is T₂>T_2.5>T₃, the velocity is T₃>T_2.5>T₂. When the groove is T type and the diameter of the rotor is 46 mm, at the range from 0o to 360o in groove, the pressure in the groove of different speeds is T₂>T_2.38>T_2.76, the velocity is T_2.76>T_2.38>T₂.The single factor experimental study of the spinning process of cotton polyurethane rotor spinning composite yarn and cotton polyester rotor spinning composite yarn were carried out respectively. The linear relationship between yarn performance and air velocity were obtained by combining the experimental results of the rotor speed with the composite yarn and the simulation results of the rotor velocity on the airflow inside the rotor. The results indicate that when the diameter of the rotor is 46 mm and the groove is T type, with the increase of rotor speed, the breaking strength and the unevenness of composite yarn are positively associated with the airflow velocity, the breaking elongation and the hairiness of composite yarn are negatively associated with the airflow velocity. When the filament draw ratio was 3.6 and the twist factor was 460, it is illustrated that the twist factor increases and the breaking strength and breaking elongation of the cotton polyurethane composite yarn increase gradually, the unevenness and the hairiness of the cotton polyurethane composite yarn decrease gradually. When the rotor speed was 20000 r/min and the twist factor was 460, it is shown that the breaking strength and the irregularity of the cotton polyurethane composite yarns increase with the increase of the rotor speed, and the elongation at break and hairiness decrease gradually. When the filament draw rate was 1.11 and the twist factor was 460, it is indicated that the breaking strength, breaking elongation, unevenness and hairiness of the cotton polyester composite yarn decrease with the increase of the filament overfeeding rate. When the rotor speed was 20000 r/min, the filament draw rate was 1.11, it is illustrated that the breaking strength, breaking elongation, unevenness and hairiness of the cotton polyester composite yarn increase with the increase of the twist factor. And the breaking strength and the unevenness of the dryness of the cotton polyester composite yarn increase gradually, and the elongation at break and hairiness decrease gradually.Based on the single factor experimental results of the spinning process of cotton polyurethane rotor composite yarn and cotton polyester rotor composite yarn, the orthogonal design experiments were carried out on the cotton polyurethane rotor composite yarn and cotton polyester rotor composite yarn. The optimum parameters of the process parameters were obtained. The results showed that the best process parameters of cotton polyurethane composite yarn are as follows: the filament draw ratio was 3.2, the twist coefficient was 440, and the rotor speed was 25000 r/min. The optimum process parameters of the cotton polyester composite yarn are as follows: the filament overfeed rate is 1.17, the twist coefficient is 450, and the rotor speed is 20000 r/min.