Aerodynamic Characteristics of Pressure-Pad Air Bars

Abstract

Air-flotation ovens are widely used for noncontact support and drying of coated paper and plastic films (generically called webs). The main components in typical air-flotation ovens are air bars which have slot nozzles or holes through which hot air jets are ejected. Problems in air-flotation drying techniques include sideward motion of the web, web flutter, and contact between the web and air bars. The key to analyzing these problems is to determine the aerodynamic forces on the web. This paper discusses the aerodynamic forces generated by pressure-pad-type air bars, each of which has two slot nozzles. Ground-effect theories, which were originally developed for the design of hovercraft, are re-examined. The theories are compared with the measured values of the aerodynamic forces for typical air bars. It is shown that ground effect theories can be applied to pressure-pad-type air bars if we properly define the equivalent values of the ground effect variables, which include thickness of the air jet, flotation height, ejection angle of the air jet, and the effective total pressure of the air jet. [S0021-8936(00)02801-4]

Flotation Height Prediction under Stable and Vibration States in Air Cushion Furnace Based on Hard Division Method

“…However, in the actual production process, the flotation height of strip usually is low when the strip is under stable state. erefore, the thickwall jet theory is more suitable for stable state flotation height prediction [10]. e thick-wall jet theory has a prerequisite assumption: due to the effect of centrifugal force, there is a pressure gradient field with uniform change in the thin-layer profile of air cushion [10].…”

“…erefore, the thickwall jet theory is more suitable for stable state flotation height prediction [10]. e thick-wall jet theory has a prerequisite assumption: due to the effect of centrifugal force, there is a pressure gradient field with uniform change in the thin-layer profile of air cushion [10]. e requirements of force balance are Mathematical Problems in Engineering…”

“…e strip is floated stably in air under stable state while the strip is fluttering in air under vibration state. For the above reasons, we propose a flotation height prediction model based on the hard division method, which can further divide the working states into stable state and vibration state [1,10].…”

“…Existing flotation height hybrid models under stable state were established on thin-wall jet theory. Some studies have also proved that the thin-wall jet theory is less efficient than thick-wall jet theory in the low flotation height circumstance [10]. To the best of authors' knowledge, a flotation height hybrid model based on the thick-wall jet theory has not been reported in the literature.…”

Paper submission

“…Up to the present time, many studies have been conducted on a plate floating by air pressure. Chang and Moretti [2] studied the steady pressure caused by air flow on the lower side of the plate. For the self-excited vibration, Ishihara and Eto [3] presented that the self-excited vibration in a vertical direction (floating direction) occurs in a plate floating by air pressure.…”