This paper includes the authors'experiments measuring the impeller characteristics with No.15-type F. W.-flotator with guide vanes around the impeller and photographing the flow-patterns of air bubbles inside as well as outside of the impeller with a transparent No.5-type F. W.-flotator.
Major experimental results are summarized as follows;
1) By fitting pulp circulation holes to the hood plate, the flow-pattern of pulp between blades of impeller was improved and the stagnating area of air-bubbles was narrowed.
2) By enclosing the impeller with guide vanes, the flow-pattern within the impeller was found much more improved, and consequently the quantity of open air blown in were increased with the increase of exit velocity head and total head coefficient.
3) By proper selection of the guide vane and circulation hole of the hood-plate, the required inducing air capacity and pulp agitating action were found practicable with the use of rather small size impeller with comparatively low peripheral velocity and the minimum power.