Experimental Aerodynamic Analysis of Converging Free Jets

The setup of the converging jets is commonly used in the manufacture of meltblown fibers. This requires forced airflow through small channels angled toward each other until meeting at the exit of the die. The emerging air jets impinge while molten polymer is extruded and becomes entrained in the air flow to be collected downstream as a thin cooled fiber.

The experimental analysis of converging free jets was examined to reveal characteristics of the flow field. A hot-film anemometer was used to gather and analyze the corresponding data for two separate meltblown fiber dies. These were examined and compared to each other as well as previous computational fluid dynamics studies of similar setups.

A traverse system was used to position the anemometer probe while measurements of the mean velocity and turbulence intensity were obtained at varying positions throughout the flow fields. This data was analyzed and compared to existing studies and theoretical prediction and was found to agree with existing computer models by showing three distinct regions: the first zone where each emerging jet maintains individual velocity profiles; a second mixing zone of maximum turbulence and an intermediate velocity profile; and a third zone where the individual jets are no longer present and the velocity profile becomes characteristic of a theoretical single emerging jet of similar mass flow rate.