Abstract
A twin-volute scheme is introduced to mitigate the circumferential structural unevenness endured by commonly used vertical centrifugal pumps. Emphasis is placed upon flow characteristics associated with twin volutes and radial hydraulic forces acting upon twin volutes. For comparison, a single-volute centrifugal pump with an identical impeller is investigated as well. Large eddy simulation is employed to extract details from three-dimensional flows in the two pumps at various flow rate conditions. Momentary radial hydraulic forces acting upon the volute are calculated based upon static pressure distributions over the volute wall. Characteristic pressure fluctuation frequencies are obtained as well. Advantages of twin volutes in improving circumferential evenness of the pump and accommodating situations of large flow rates are corroborated. The strip of high static pressure adjacent to the volute wall serves as an evident indicator of the suitability of twin volutes. Relative to the conventional volute, twin volutes undergo considerably small radial hydraulic forces, which are reduced consistently as flow rate increases. Another unique feature of twin volutes lies in the similar relationship between pressure fluctuation amplitude and characteristic frequency among the monitored points near the volute throat. And the overall amplitude of pressure fluctuation corresponding to blade-passing frequency increases with flow rate, as deviates considerably from the generalized tendency associated with the conventional volute.
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