INVESTIGATION OF CAVITATING AND NONCAVITATING FLOW IN A CENTRIFUGAL PUMP USING PIV TECHNOLOGY

للكاتبين :

A.M. El-Zahaby, A. Khalil, E.A. El-Shenawy and M.I. Amr

Department of Mechanical Power Engineering, Tanta University, Egypt

ABSTRACT

The internal flow structure in a centrifugal pump impeller is investigated using Particle Image

Velocimetry (PIV). The measurements are performed in a Perspex model of an industrial centrifugal

impeller employing fluorescent seeding particles to give full access to near-wall flows. A large number

of velocity vector maps are acquired by conditional sampling in a vertical constant-width plane

between hub and shroud of the impeller. The field of view in effect is the full impeller passages.

Instantaneous and ensemble-averaged velocity vector maps are transformed to the moving frame and

analyzed for the purpose of identifying steady and unsteady flow phenomena at different flow rates

with the main focus on off-design conditions as well as the cavitation conditions. High levels of

turbulence are confined to near-wall regions along the inlet and outlet surfaces of the impeller.

Experimental results from PIV system, concerning pump characteristics and performance breakdown,

were compared at different flow conditions. Appearing types of cavitation and the spatial distribution

of vapor structure within the runner are also analyzed. Analysis of the obtained data concerning

cavitating flow, turbulent kinetic energy or turbulence intensity may be taken as a parameter for

detecting cavitation. The significance of this study appears in understanding the turbulence

characteristics inside the centrifugal pump impeller. Moreover, it can help in developing flow

prediction codes.

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