Numerical simulation and experimental investigations of air drawing model and air jet flow field model in wide slot positive pressure spunbonding process

摘要

An air drawing model of polymers and a model of the air jet flow field model in wide slot positive pressure spunbonding process are established. The air jet flow field model is solved by means of the finite difference method. The numerical simulation computation results of distributions of the air velocity match quite well with the experimental data. We find that the variation of the density and the specific heat capacity of polymer melt at constant pressure with polymer temperature have much effects on fiber diameter. The newly developed formulas were incorporated into a spunbonding theoretical model to predict the fiber diameter of nonwoven web. The air drawing model of polymer is solved with the help of the distributions of the air velocity measured by a Particle Image Velocimetry (PIV). The predicted fiber diameters agree with the experimental data well. It can be concluded that the higher air pressure, higher air velocity and air temperature can yield the finer fibers diameter. The higher inlet pressure and smaller jet angle will all cause higher x-axis position of air velocity and air pressure, which are beneficial to the air drawing of the polymer melt and thus to reducing the fiber diameter.