A new three-dimensional aerofoil diffuser for centrifugal compressors

Abstract

Abstract

Aerofoil diffusers have been extensively used in industrial centrifugal compressors. However, these diffusers are two-dimensional and have fixed solidity in the spanwise direction. Two types of two-dimensional aerofoil diffusers exist: the first characterized by a solidity value less than 1 (low solidity diffuser) and the second characterized by a solidity value greater than 1 (high solidity diffusers). In this article a new three-dimensional aerofoil diffuser is introduced. This diffuser has a varying solidity and stagger angle in the spanwise direction as well as a varying lean angle along the streamwise direction. The use of these three-dimensional configurations leads to the development of an aerofoil diffuser that combines the wide operating range characteristic of the low solidity diffusers with the high performance that is characteristic of the high solidity diffusers. Experimental and numerical analyses of several impeller—diffuser configurations are presented. The analyses are performed between the newly introduced three-dimensional aerofoil diffuser and the conventional diffusers with high and low solidities. The results of the analyses are presented in terms of the aerodynamic performance of both the diffusers and the overall stage performance. The analyses performed indeed indicate the superiority of the proposed new diffuser geometry over the analysed conventional aerofoil diffusers in terms of extending the operating range of the compressor stage as well as improving its efficiency.