Effect of vessel scaleup on the hydrodynamics of a self-aerating concave blade impeller

✍ Scribed by C.D. Rielly; G.M. Evans; J.F. Davidson; K.J. Carpenter

• Publisher: Elsevier Science
• Year: 1992
• Tongue: English
• Weight: 802 KB
• Volume: 47
• Category: Article
• ISSN: 0009-2509
• DOI: 10.1016/0009-2509(92)85050-l

✦ Synopsis

A theoretical model has been developed to predict the pressure at the gas outlet of a gas-inducing impeller and to determine the minimum speed at which gas induction occurs, for a given impeller design and submersion depth. The model also predicts the flow rate of gas induced at higher impeller speeds, by balancing the pressure reduction due to flow over the blades, against pressure losses associated with the flow of gas and bubble formation. Pressure measurements for an impeller moving in single-phase (prior to gas induction) were used to determine independently the model constants for a concave impeller. These constants were identified as a blade slip factor and a pressure coefficient and were shown to be independent of Reynolds number (in the turbulent regime) and constant over the range of submersion depths used in practice_ The model predictions for the minimum induction speed were in good agreement with experiments for a concave impeller at a number of angles of attack and in,@ous vessel geometries_ Gas flow rate measurements at higher impeller speeds indicated that the pressure driving force was a function of the detached bubble radius, and providing this dependence was known the model could be used to predict the rate of gas induction.