FRI-9.2-1-THPE-01
SPECIFICS IN THE OPERATION OF CENTRIFUGAL PUMPS WHEN TRIMMING THEIR IMPELLERS
Abstract
In order to reduce costs in the production of centrifugal pumps, as well as to expand their use, manufacturers reduce only the outer diameter D2 of a pump impeller, remaining the pump flow elements unchanged (the so-called "impeller trimming"). In their catalogs, these companies also present the new pump operating curves for the corresponding outside diameter of the trimmed impeller. When trimming an impeller, the geometric similarity (affinity) of the pump is violated, since only the impeller outer diameter is reduced, while the other typical sizes remain the same. Therefore, the laws of similarity (affinity laws), used in turbomachines, have no relevance (correspondence) when trimming a pump impeller. In order to clarify how the pump parameters vary when trimming their impellers, the materials (catalog data) provided by some centrifugal pump manufacturers, such as GRUNDFOS, KSB and VIPOM, are studied. Based on the analysis performed, it was found that the formulas (equations) proposed in the available literature sources concerning the determination of a pump operation when it operates with a trimmed impeller does not provide good corresponding to its actual operation. The exponents concerning the flow rate and head obtained at different rates of trimming are calculated and presented graphically. They vary widely both in terms of their specific speed of rotation, as well as in accordance to the manufacturing specifics of the different companies-producers.
Keywords
centrifugal pump, cutting of the impeller, flow rate, pump head, degree of trimming
REFERENCES
- промяната на показателите зависи от много фактори, които не могат да бъдат предсказани. Затова, за предпочитане е работното колело да се подрязва на стъпки. По този начин се намалява рискът от пропускане желания работен режим, ако подрежем в по-голяма степен работното колело. ИЗЛОЖЕНИЕ При намаляване на относителния диаметър на подрязване D D *2
- Aizenshchein, M. D. (1957). Centrifugal pumps for oil industry. Gostoptekhizdat. M. 1957. (Оригинално заглавие: Айзенщейн, М. Д. Центробежные насосы для нефтяной примышлености. Гостоптехиздат. М. 1957).
- GRUNDFOS https://www.lenntech.com/Data-sheets/Grundfosliterature-NB-NBE-NK-NKE-GB-L.pdf.
- Gülich J. Fr.(2020). Centrifugal Pumps, Fourth Edition, Springer-Villeneuve, Switzerland, 2020, ISBN 978-3-030-14787-7. KSB Calculation of parameters of centrifugal pumps (Оригинално заглавие: Расчёт параметров центробежных насосов . KSB) https://www.rsnasos.ru/info/ksb-rassch-param-centrobej-nasosov.pdf.).
- KSB Shanghai Pump Co., Ltd https://www.agrolinkirriga.com.br pdf/motobombas/KSB- ETANORM.pdf.
- Lomakin D.A., Korotkov V.V. (2017). Correction of characteristics of centrifugal pumps by cutting the impeller. MSTU them. N.E.Bauman, 2017 (Оригинално заглавие: Ломакин Д.А., Коротков В.В. Корректировка характеристик центробежных насосов за счёт подрезки рабочего колеса . МГТУ им. Н.Э.Баумана , 2017).
- Nikolova D. (2022). Calculating the performance of a centrifugal pump when cutting its impelle. PROCEEDINGS OF UNIVERSITY OF RUSE - 2022, volume 61.
- Plaiderer K.(1960). Blade machines for liquids and gases, M., Mashgiz, 1960-683 (Оригинално заглавие: Плайдерер К. Лопаточные машины для жидкостей и газов, М., Машгиз, 1960-683, прев. от немски).
- Popov G., Klimenntov Kl., Nikolova D. (2021). Analysis of the methods for trimming the impellers of Centrifugal Pumps. 60<sup>th</sup> Science Conference of Ruse University - SSS, Bulgaria, 2021.
- Stepanov A.I. (1960) Centrifugal and axial pumps. M., Mashgiz, 1960, 463 (Оригинално заглавие: Степанов А. И. Центробежные и осевые насосы. М., Машгиз, 1960, 463, прев. от англ.). VIPOM AD. Centrifugal single-stage pumps, type E, E-M. Catalog (Оригинално заглавие: Помпи центробежни едностъпални, тип Е, Е-М. Каталог - ВИПОМ- АД).
- Zlatarev. P. (1979). Turbo pumps and fans. Technique, S.1979 (Оригинално заглавие: Златарев П. Турбопомпи и вентилатори. Техника, С. 1979).