Wyniki wyszukiwania - BazTech

1

Analiza przepływu kawitacyjnego w pompach

Sedlar M., Zima P., Pozdisek T.

Pompy, Pompownie

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2009

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nr 2 (133)

40-43

PL

Prezentacja pracy badawczej o charakterze poznawczym i użytkowym. Cenny przyczynek do oceny stanu rozwoju kawitacji w palisadach łopatkowych oraz przewidywania konsekwencji w postaci załamania charakterystyki i wyznaczania wartości NPSH3.

EN

Presentation of research work offering cognitive and utilisable values. A valuable contribution to the assessment of condition of cavity development in blade cascades and forecasting of consequences of characteristics collapse and NPSH3 value.

2

Numerical analysis of cavitated flows in mixed-flow pump impellers

Sedlar M., Marsik F., Safarik P.

Zeszyty Naukowe Politechniki Świętokrzyskiej. Mechanika

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2003

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Z. 77

57-64

EN

This paper deals with the flow model based on the Navier-Stokes computation and the simulation of bubble dynamics in the flow field, solving the Rayeigh-Plesset equation alongflow characteristics. No interaction between bubbles is considered. The initial bubble sizedistribution is based on a precribed distribution law and the initial void fraction. The flowpast the blades of mixed-flow pump impellers is investigated including the tip leakage flowsfor three different impeller configurations, aimed to predict the impeller configuration influence on cavitation phenomena, especially the blade surface regions endangered with the cavitation phenomena, especially the blade surface regions endangered with the cavitation erosion.

3

Condensation and cavitation in water and water mixtures

Marsik F., Delale C., Sedlar M.

Archives of Thermodynamics

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2003

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Vol. 24, no 1

3-16

EN

The aim of this investigation is to reconsider the classical theory of homogeneous condensation and bubble nucleation by using real properties of fluids and non-equilibrium (dissipative) effects. To find out the influence of a chemical composition on the surface tension and consequently on the nucleation work and further to elucidate how the nucleation barrier is affected by the irreversible processes on the bubble surface the theoretical analysis is used. Both these effects are important for the nucleation and it is shown that they can increase (for condensation) the nucleation work. The theory is suitable both for pure substances and for their mixtures. The emphasis is laid on water condensation, boiling and cavitation.

4

Numerical investigation of flow in mixed-flow pump with volute

Sedlar M.

TASK Quarterly : scientific bulletin of Academic Computer Centre in Gdansk

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2001

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Vol. 5, No 4

595-602

EN

The work considers the modelling of flow in a complete mixed-flow pump with volute, including tip leakage flows, using both quasi-steady and true transient models of rotor/stator interaction. The CFX-TASCflow CFD package from AEA Technology is applied to calculate flows for a wide range of flow rates from about 0.2 to 1.4 Q/sub 0pt/. Fairly detailed flow structures have been predicted based on the flow rates, especially impeller inlet recirculation and separation on the suction side of the blades for suboptimal rates of flow, as well as strong secondary flows and separation in the volute for off-design conditions. The rotor/stator interaction influence on flow phenomena both in the impeller and volute have been investigated with very interesting results, providing good insight into the dynamics of flow close to the volute tongue. Based on the computational results, pump performance curves (Q-H, Q- eta /sub h/ and Q-P, eta /sub h/ being the hydraulic efficiency) have been obtained. The data from this numerical investigation have been used to improve the inlet part of the impeller blades, especially close to the tip. The geometry modifications have resulted in reduced cavitation in the impeller as well as noise at suboptimal rates of flow.