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Partload Operation, Impact of 3-D Flow Phenomena Performance

  • Johann Friedrich GülichEmail author
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Abstract

A pump working significantly below the best efficiency flow rate is said to operate at partload. At low specific speeds this can be roughly assumed at q* < 0.8, at high nq below q* < 0.9. Since blade inlet angles and channel cross sections are too large for the reduced flow rate, flow patterns during partload operation fundamentally change compared with the design point. The flow becomes highly 3-dimensional since it separates in the impeller and the collector. Finally, recirculations are observed at impeller inlet and outlet at sufficiently low flow. An easy means to obtain information on the impeller flow are stroboscopic observations of tufts. Flow patterns in a radial impeller of nq = 22 gained in this way are shown in Fig. 5.1 [B.20]. It can be seen that the flow is attached at q* > 0.8 while increasingly large zones with separation and recirculation are observed at a lower flow rates. Similar flow patterns were found on impellers of nq = 26 and 33.

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Authors and Affiliations

  1. 1.VilleneuveSwitzerland

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