Characteristics of Air Film Thickness and Flow Visualization for Transporting Film

Abstract

Continuous flexible thin material, such as paper, textiles, and plastic films, are referred to as webs. At present, web machines are used in various fields. However, a number of problems regarding web handling industries remain to be solved. Generally, webs are transported through rollers. When a web is transported at high speed, the surrounding air enters the gap between the web and the roller and forms an air film. The air film prevents scratches and stains because it eliminates the contact between the web and the roller. However, the air film generates slip due to the reduced traction, which is a serious problem for web production. Therefore, control of the air film thickness has become important. In the present study, measurement of the air film thickness is conducted using a PET film as the web. An experiment is carried out to examine the effect of changing the relative velocity between the web and roller. In addition, flow visualization is conducted in the inlet and outlet areas of the web wrap region using particle image velocimetry (PIV). As a result, the effect of the air flow between the web and the roller on the air film formation and the characteristics of the flow near the inlet and outlet areas are clarified.

Keywords

• pressure distribution
• flow visualization
• web handling
• air film thickness
• transport speed