Comparison of Periodic Flow Fields in a Radial Pump among CFD, PIV, and LDV Results

Jianjun Feng,H J Dohmen,F.-K Benra

doi:10.1155/2009/410838

Jianjun Feng, H J Dohmen + Show 1 more

Open Access

https://doi.org/10.1155/2009/410838

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Abstract

The interaction between the impeller and the diffuser is considered to have a strong influence on the unsteady flow in radial pumps. In this paper, the unsteady flow in a low specific speed radial diffuser pump has been simulated by the CFD code CFX-10. Both Particle Image Velocimetry (PIV) and Laser Doppler Velocimetry (LDV) measurements have been conducted to validate the CFD results. Both the phase-averaged velocity fields and the turbulence fields obtained from different methods are presented and compared, in order to enhance the understanding of the unsteady flow caused by the relative motion between the rotating impeller and the stationary diffuser. The comparison of the results shows that PIV and LDV give nearly the same phase-averaged velocity fields, but LDV predicts the turbulence much clearer and better than PIV. CFD underestimates the turbulence level in the whole region compared with PIV and LDV but gives the same trend.

Highlights

The internal flow developing in a radial diffuser pump is extremely complicated and highly turbulent, caused by streamline curvatures, system rotation, flow separations, rotor-stator interaction, and turbulence effects
All the results presented here are limited to the design operating point Qdes and at midspan, that is, at the half blade height
The velocity and turbulence fields obtained from CFD, Particle Image Velocimetry (PIV), and Laser Doppler Velocimetry (LDV) are compared both qualitatively and quantitatively at the design operating point

Summary

Introduction

The internal flow developing in a radial diffuser pump is extremely complicated and highly turbulent, caused by streamline curvatures, system rotation, flow separations, rotor-stator interaction, and turbulence effects. The rotorstator interaction is assumed to have an important influence on the time-variant flow behavior in the case of a small radial gap between the impeller trailing edge and the diffuser leading edge [1]. PIV has the advantage of measuring the whole flow field instantaneously, whether it is steady or unsteady. PIV has been widely applied in the flow measurements in radial pumps. Akin and Rockwell [9] applied PIV to study the impeller wake and its interaction with diffuser vanes. Sinha and Katz [10] used PIV results to identify the unsteady flow structure and turbulence in a radial pump. Compared with PIV, Laser Doppler Velocimetry (LDV) is more time-consuming but gives more accurate results due to the measurement directly on the points of interest. LDV measurements conducted in radial pumps have been reported by Akhras et al [15], Hajem et al [16], Pintrand et al [17], and Akhras et al [18]

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Results

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