Energy and Power En gi neering, 2011, 3, 29-33

doi:10.4236/epe.2011.31005 Published Online February 2011 (http://www.SciRP.org/journal/epe)

Copyright © 2011 SciRes. EPE

Predication of 3-D Viscous Flowfield of a Centrifugal

Impeller

Limin Gao, Xudong Feng, Jian Xie

School of Power and Energy, Northwestern Polytechnical University, Xi’an, China

E-mail: gaolm@nwpu.edu.cn

Received September 10, 2010; revised November 5, 2010; accepted November 15, 2010

Abstract

A three-dimensional viscous code has been developed to solve Reynolds-averaged Navier-Stokes equations.

The governing equations in finite volume form are solved by two-step Runge-Kutta scheme with implicit

residual smoothing. The eddy viscous is obtained using the Baldwin-Lomax model. A prediction of the 3-D

turbulent flow and the performance in the “all-over controlled vortex distribution” centrifugal impeller with a

vaneless diffuser has been made for the compressor at design and off-design condition. The predicted effi-

ciency is a little higher than the experiment data. These results suggest that the present calculation code is

able to determine the flow development in the impeller and also the turbulence model in the centrifugal im-

peller should be improved.

Keywords: Centrifugal Impeller, Aerodynamic Performance, 3-D Viscous Flow Calculation, Design &

off-Design Conditions

1. Introduction

Centrifugal compressors are used widely in industry due

to their advantages of simple structure and high-pressure

ratio. However, their efficiency and stability are ad-

versely influenced by the present of impeller exit flow

non-uniformity. In recent years, as a result of improve-

ments in experimental techniques and numerical methods,

it has been possible to avoid the non-uniformity of exit

flow field in order to obtain improved efficiency and

stability of an impeller. The work of Eckardt’s [1] and

Krain’s [2] are most representative in all related experi-

mental research. Their studies indicated that both com-

plicated secondary flows and separated boundary layer

would cause the radial and circumferential non-uniform

flows at the outlet, and consequently the performance of

the centrifugal compressor decreases. Meanwhile, some

numerical codes have also been developed to study the

flowfield in centrifugal compressor by other researchers.

Most of them [2-4] have provided the detailed flowfield

to understand the complicated flow. However, CFD is

still a little immature and does not reach the engineering

implementation level. Further research is necessary to

develop a more accurate and faster, numerical predicting

code, which will provide the sophisticated tool to predict

the aerodynamic performance of a high-speed centrifugal

compressor for designing an impeller with higher pres-

sure-ratio and efficiency.

In the present work, a 3-D turbulent code has been

developed, and the prediction of 3-D viscous flowfield of

an AOCV centrifugal impeller has been carried out.

Therefore, it is hoped that the present study will provide

a useful predication tool to aid in the future experimental

work and the industrial design.

2. AOCV Centrifugal Impeller

The air compressor, which is applied in a large-scale

air-separation plant, is produced from SER Turboma-

chinery Research Center of the Xi’an JiaoTong Univer-

sity. Its impeller is a three-dimensional centrifugal im-

peller which is design using the All-Over Controlled

Vortex Distribution designing theory.

The impeller is shrouded and has 19 full blades with

an exit backswept of 50 degs. The inlet diameter is 0.222

m and the inlet blade height is 0.0606m. The exit diame-

ter is 0.340 m and the exit blade height is 0.0272 m. The

design speed of 16360 rpm gives a rotor exit tip speed of

290 m/s. The design mass flow rate is 2.8 m3/s at the

standard inlet conditions of 101, 325 N/m2 and 288.15 K.

The rotor tip Reynolds number (U2D2/ν) is 1.42 × 106.

The impeller is showed in Figure 1.