Calculation of centrifugal pump critical NPSH

Аuthors

Fedoseev S. Y.^1*, Timushev S. F.^1**, Kuznetsov A. V.^2***, Panaiotti S. S.^3****

1. Moscow Aviation Institute (National Research University), 4, Volokolamskoe shosse, Moscow, А-80, GSP-3, 125993, Russia
2. Nauchno-proizvodstvennoe ob’edinenie “Gidromash”, 2, 2-ay Mytischenskay , St., Moscow, 195008, Russia
3. Kaluga branch of Moscow State Technical University named N. E. Bauman, 2, Bazhenov str., Kaluga, 248000, Russia

*e-mail: it202mai@gmail.com
**e-mail: TimushevSF@mai.ru
***e-mail: 195008@mail.ru
****e-mail: panaiotti@post.ru

Abstract

In recent years, required Time Between Overhaul (TBO) of centrifugal pumps for TPS, NPP, marine and other facilities is up to 40,000 hours. One of the main factors limiting the growth of the TBO is cavitation erosion of impeller blades. NPSH is usually chosen with respect to the cavitation flow break operation mode. However, this NPSH choice not guaranteed to work without cavitation erosion due to unsteady flow behavior at the impeller inlet. In this regard, it suggests ways to calculate NPSH of the cavitation inception. On the basis of the published experimental data the inception cavitation coefficient empirical formula is derived. Furthermore three-dimensional unsteady turbulent flow in the impeller validated with experimental data published shows cavitation inception operation modes on different flow rates including back flow phenomena range. The described method of computer modeling can be recommended to optimize the pumps against cavitation erosion. Cavitation flow break NPSH value calculated from the equations of flow, energy and momentum for the plane cascade of plates of finite thickness. The data obtained are generalized to the circular cascade of centrifugal impeller. For optimization by flow break NPSH the Rudnev analytical formula and Shemel & Shapiros empirical formula are recommended. All this data give one the opportunity to reasonably choose the centrifugal pump NPSH required.

Keywords:

сentrifugal pump, cavitation erosion, NPSH, cavitation inception, cavitational flow break

References

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