Volutes are often used on the discharge of a centrifugal pump and compressor to provide efficient gathering of flow moving radially outward and direct to a single tangential exit point. To provide this efficiency, volutes are sized to provide near zero circumferential static pressure distribution at the Best Efficiency Point (BEP). However, as the compressor or pump operates away from BEP, a circumferential variation in static pressure is created within the diffuser and is felt by the impeller. This non-uniform static pressure can also be felt in the journal bearings. Accounting for this radial loading is essential when sizing journal bearings for the pump or compressor to work properly. The volute has been the subject of numerous extensive theoretical, numerical and experimental studies, because the volute strongly affects the overall performance, stability, operating range and the location of the best efficiency point of the pump or compressor. This paper reviews the status of methods for predicting the volute-induced radial force and also attempts to provoke renewed interest and possibly encourage more work to contribute towards a more accurate prediction of the volute-induced radial force. Both pumps and compressor are now being built with increasing pressure ratios, higher speeds and larger sizes, thus giving importance to the need for more accurate radial force prediction methods.

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