Analysis of a Melt-Blowing Die: Comparison of CFD and Experiments

The flow field resulting from two similar converging-plane jet nozzles was studied using a computational fluid dynamics approach that was validated through experimental data. The case in which the nozzles were near each other (blunt die) and the case in which there was no space between the nozzles (sharp die) were both considered. Such rectangular nozzles are used commercially to produce polymeric fibers in melt-blowing processes. The k−ε turbulence model and the Reynolds stress model were used. The model parameters were calibrated by using the experimental data; accurate model predictions resulted from this calibration. The flow field downstream from the blunt die was found to exhibit (a) a region in which each jet has its own identity; (b) a merging region, which includes a maximum in turbulence intensity; and (c) a self-similar region. The flow field for the sharp die exhibited only the latter two regions of development. The behavior of alternative die designs, with different jet angles, was also examined. As the jet angle becomes sharper, the mean velocity under the die increases, but at the same time, the turbulence becomes stronger.