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Inlet impeller rounding in pumps as turbines: An experimental study to investigate the relative effects of blade and shroud rounding

Doshi, Ashish and Channiwala, Salim and Singh, Punit (2017) Inlet impeller rounding in pumps as turbines: An experimental study to investigate the relative effects of blade and shroud rounding. In: EXPERIMENTAL THERMAL AND FLUID SCIENCE, 82 . pp. 333-348.

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Official URL: http://dx.doi.org/10.1016/j.expthermflusci.2016.11...

Abstract

This paper is objected to bring out an unbiased and detailed hydraulic response study in pumps as turbines due to blade rounding, inner and outer shroud rounding of the impeller inlet through high quality measurements of macroscopic parameters. To begin with a theoretical model is proposed where the hydraulic losses are categorized as flow zone and no-flow zone types, while suitable assumptions are made to the shaft and runner (Euler) torque. Four centrifugal pumps having specific speed in the range of 19-54 rpm are selected for this 3-stage impeller rounding investigation. All pumps had backward vane impeller designs. The blade rounding showed greater reduction of flow zone losses compared to increase of runner torque resulting in an efficiency rise of 1-1.5%, while inner shrouds have shown evidence of decrease in losses but an inconsistent behavior of runner torque gains. The final rounding stage at the outer shrouds displayed traces of proof of non-flow zone hydraulic optimization. The consolidated rounding effects were compared to results of other researchers which again showed concurrence and consistency. The paper evokes a sentiment that the technique of fixed geometry optimizations of backward vane impeller has been saturated given that the maximum efficiency rise is only in the range of 1-2.5%., even though the total hydraulic losses constitute 25-30% of the total energy (head) since the achieved best efficiency after modification ranges between 65% and 75%. Therefore, the paper recommends a calibrated methodology to change the backward vane angle so that the inlet relative velocity aligns with the blade and the strong wakes are reduced, which could reduce losses by 5-10%. To conclude the paper pragmatically looks towards the limited scale of PAT application compared to pumping and proposes the study of rounding effects on pump operation to see if there is any positive alleviation of performance, which could have a greater benefit to industry and society.(C) 2016 Elsevier Inc. All rights reserved.

Item Type: Journal Article
Additional Information: Copy right for this article belongs to the ELSEVIER SCIENCE INC, 360 PARK AVE SOUTH, NEW YORK, NY 10010-1710 USA
Department/Centre: Division of Mechanical Sciences > Centre for Sustainable Technologies (formerly ASTRA)
Depositing User: Id for Latest eprints
Date Deposited: 09 Mar 2017 05:59
Last Modified: 09 Mar 2017 05:59
URI: http://eprints.iisc.ac.in/id/eprint/56348

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