Computational Investigation on Deswirl Vanes for Multistage Centrifugal Compressors

Abstract

The goal of this project is to report on some computational investigations about the return flow passages. The return flow channel provides the connection and carries the flow between two stages of a multistage centrifugal compressor. Of course, deswirl vanes are indispensable between the inlet and outlet section, because usually the inlet flow angle, which comes from the impeller, is 70° -75° measured from radius and the downstream flow angle should be axial, for the next stage. Generally, the shape of this unconventional blade is unique; it is not possible to choose it from any catalogues. During the design procedures, a couple of new blade design techniques have been developed; among them one is based on a zero circulation over the control surface, between two blades with the meaning of CBL (constant blade loading) [14]. The purpose of this investigation is to construct a 3D blade for the return passage. In addition, a system of programs for UNIX was developed to help us to communicate between the different software. The next step is to use the inviscid inverse design program to make the most relevant blade; provided by the CBL design, as perfect as possible and introduce negative and positive lean to improve the design specifications. Finally, we should analyse the configuration with a 3D Navier-Stokes solver to have some conclusions about the new blade geometry. Of course, in the design process, the loss coefficient and pressure recovery factor are the two main parameters, which are always taken into consideration to check the correctness of the design.