CFD Analysis of Effect of Diffuser Vane Setting Angle and Shape on the Performance of a Centrifugal Compressor Stage

This paper describes the computational results on the performance of a centrifugal compressor stage with Vaneless diffuser (VLD) and low solidity vaned diffuser (LSVD) by varying blade shape and its setting angle. The centrifugal compressor stage configuration consists of a 2-D impeller with a diffuser. Analysis was conducted for VLD and four different blade shapes of LSVD namely Un-cambered constant thickness flat plate (FP), Cambered curved arc constant thickness plate (CCAP), Un-cambered aerofoil profile NACA 0010(NACA 0010) and Cambered aerofoil profile NACA 2410 (NACA 2410) at five different setting angles ranging from 16° to 32° in steps of 4° for each blade. The study is conducted at five different flow coefficients, at 0.8, 0.9, 1.0, 1.1 and 1.2 of design mass flow rate representing the design and off design cases for VLD and LSVD. CFD results are validated with experimental results for stages with VLD and LSVD for certain chosen performance parameters such as head coefficient, stage input power and exit flow angle. The computational results indicate that variations in diffuser vane geometry and its setting angle causes changes in all significant performance parameters like the total head coefficient, total-to-static stage efficiency, power coefficient of the stage and static pressure recovery coefficient of the diffuser. Contour plots were generated from CFD results and analyzed for better understanding of effect of diffuser vane shape and its setting angle on the performance of the centrifugal compressor. As a result of this study, it can be concluded that the centrifugal compressor shows improved performance characteristics for chosen blade shape of low solidity vaned diffuser than VLD.