Polymer Drawing Model In The Combined Air Flow Field Of The Melt Blowing Process

Melt blowing is a polymer laid nonwoven technology and one of the main methods for producing superfine fibers. In this process, the polymer melt is attenuated into superfine fibers by air which is of high temperature and velocity. Therefore, distributions of air velocity and temperature have great effect on the final fiber diameter. An converging-diverging nozzle is installed below the melt blowing main nozzle in order to make the air flow field more advantageous to drawing. The combined air flow field is constructed including the main nozzle air flow field(dual slot die) and converging diverging air flow field.In this thesis, the combination of the air flow field and the singleness of the air flow field are simulated. The combination of the air flow field is measured in experimental method. The one-dimensional model of polymer drawing and the two-dimensional model of polymer drawing are constructed. The polymer drawing models are solved numerically.The results of solution are analyzed. This thesis consists of three parts:In part one, the combined and single model of the air flow field are established and simulated numerically. The distributions of the air velocity and temperature are obtained.The simulation results of them are analyzed comparatively. The results show that the geometry of combination flow field model extends the process of polymer drawing by delaying the attenuation of air velocity and temperature. An IFA300 hot wire anemometer is employed to measure the modified melt blowing equipment experimentally. The simulated results are compared with the measured results in the combination flow field model. The results show that they have an excellent agreement, which indicates that the combination flow field model is correct.In part two, the flow process of melt-blown polymer melt is analyzed in lagrange method. The force and heat transfer of polymer strips are analyzed. On the basis of this, the momentum equation and energy equation are constructed. The one-dimensional model ofpolymer drawing and the two-dimensional model of polymer drawing are established.In part three, the simulated air velocity and temperature are introduced into the polymer drawing model. The model is solved numerically. The change trend of the fiber diameter of the two flow field model is obtained and compared. The results show that the drawing effect of the combination flow field model is markedly better than that of the singleness flow field model. At the same time, the motion trail of polymer strips is obtained. The polymer melt wiggles continually in the process of spinning by analyzing the motion trail. The wiggling promote the drawing of polymer skips. The one-dimensional model and the two-dimensional model are compared. The results show that the two dimensional model of polymer drawing is more practically significant.To sum up, the combination of the air flow field and the singleness of the air flow field are simulated. The combination of the air flow field is measured in experimental method. The one-dimensional model of polymer drawing and the two-dimensional model of polymer drawing are constructed. The polymer drawing model is solved numerically.The results of solution is analyzed. A solid foundation for further research on the process of melt-blown polymer flow is laid.