Gas-Liquid Agitation with Closed Turbine Type Impellers Modified for Blade Geometries

M. Yoshida, M. Nakata, K. Itagaki, K. Suganuma, R. Kiyota, S. Kogami and Y. Takahashi

Abstract
An agitation impeller with shrouded blades—specifically, a closed impeller—was redesigned. A closed impeller originating from a conventional turbine-type impeller was analyzed by considering the internal liquid flow characteristics. As a result, an impeller consisting of six flat blades with radially tapered widths was developed for closed-mode operation. The modified closed impeller (6RTW-FCI) was applied to gas-liquid agitation. The flow behavior of the gas-liquid mixture in the impeller region was examined with energy considerations based on the impeller power characteristics in the gassed liquid. The internal cavities of the 6RTW-FCI generated gas bubbles that moved radially out ward due to the accelerated liquid flow produced by the impeller. The power characteristics of the 6RTW-FCI in terms of relative power consumption, which was with no sudden change for various aeration-agitation rates, supported energy conversion through the impeller, resulting in favorable gas-liquid dispersion.

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Keywords
agitation vessel, closed impeller, blade geometries, gas-liquid dispersion, power characteristics