Basic Study on Non-Contacting Support of Thin Plate by Fluid Cushion Force : Effect of Side Plates on Supporting Characteristics

Abstract

In the surface finishing line of cold steel, many surface defects are caused by contact between the roll support and strip. An optimal suface finishing process should support the strip without contact by roll since high quality steel products depend on stable operation of the running strip. In the two-dimensional flow configuration, our experimental study focuses on stability improvement of the running strip derived from the side plates installed on the pad which has nozzles with a distance much shorter than conventional setup. This study has clarified that the side plates produce the restoring force. That is, if the strip deflects from the central position, the pressure on the deflected side of the strip increases. This pressure causes the floating height of strip on the deflected side to increase. As a result, the strip tends to return to the central position by itself. Besides, it is clarified that the restoring force increases as the distance between nozzles N_b decreases, as a result of an increase in the area of pressure P_p, caused by the side plates. This is contrary to the conventional method without side plate where large lifting and restoring forces are created with a large nozzle distance N_b.