Study of Secondary Flow Modifications at Impeller Exit of a Centrifugal Compressor

Surendran Anish, Nekkanti Sitaram, Heuy Dong Kim

Andong National University, Andong, South Korea.
FMTRC, Daejoo Machinery Co. Ltd., Daegu, South Korea.
Indian Institute of Technology Madras, Chennai, India.

DOI: 10.4236/ojfd.2012.24A029                

Abstract

A computational study has been conducted to analyze the performance of a centrifugal compressor under various levels of impeller-diffuser interactions. The study has been conducted using a low solidity vaned diffuser (LSVD), a conventional vaned diffuser (VD) and a vaneless diffuser (VLD). The study is carried out using Reynolds-Averaged Navier- Stokes simulations. A commercial software ANSYS CFX is used for this purpose. The extent of diffuser influence on impeller flow is studied by keeping the diffuser vane leading edge at three different radial locations. Detailed flow analysis inside the impeller passage shows that the strength and location of the wake region at the exit of impeller blade is heavily depended upon the tip leakage flow and the pressure equalization flow. Above design flow rate, the diffuser vane affects only the last twenty percent of the impeller flow. However, below design flow rate, keeping vane closer to the impeller can cause an early stall within the impeller. Small negative incidence angle at the diffuser vane is helpful in order to reduce the losses at the impeller exit.

Keywords

Secondary Flow; Impeller; CFD; Centrifugal Compressor

Conflicts of Interest

The authors declare no conflicts of interest.

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