Abstract
Diffuser’s aerodynamic performance is crucial for the centrifugal compressors, while at present the universal principles for the optimization design of the vaned diffusers are still not available. In this paper, three vaned diffusers with different inlet Mach numbers were numerically studied in order to explore new design principles for the centrifugal compressor vaned diffusers. It proved that there are practical and effective design principles for the vaned diffuser optimizations, the performance of the vaned diffuser can be improved by carefully control of two aerodynamic parameter distributions: Tangential velocity (Vt) and Meridional velocity (Vm). The vaned diffusers with subsonic, transonic and supersonic inlet conditions were optimized with the new design principles, and the peak efficiencies were increased by 4.23%, 2.15% and 2.59%, respectively. The stage pressure ratios were increased by 3.36%, 1.39% and 6.49%, respectively, and their surge margins were also improved substantially. Finally, since the Vt and Vm could affect each other during the optimization process, an interactive optimization design procedure was also presented in this paper in order to accelerate the optimization process.
Highlights
Centrifugal compressors have the advantages of compact structure, high pressure ratio, good reliability, and wide operating range
The new vaned diffuser design principles were investigated and verified, and the main conclusions are as follows: (a) Vaned diffuser design principles: (1) The performance of the vaned diffuser can be improved by carefully control of two aerodynamic parameter distributions: Vt and Vm, which represent the capability of pressure recovery and through flow, respectively
(2) The Vm should decrease gradually and slowly along the flow passage for all inlet conditions to avoid the flow losses caused by the sudden change in the meridional velocity, and improve the flow-through capability and surge margin
Summary
Centrifugal compressors have the advantages of compact structure, high pressure ratio, good reliability, and wide operating range. They are widely used in small and medium-sized aircraft engines and gas turbines. Better aerodynamic performances and wider operating range are desired for the centrifugal compressors. HA Klassen [1] experimentally studied a pressure ratio of 6: 1 centrifugal compressor by testing a swept-back impeller. C Osbosne [2] performed a mechanical design and aerodynamic analysis of an 8: 1 centrifugal compressor. H Krain [3] carried out the numerical and experimental researches on the transonic flow fields of the centrifugal compressors, identified areas of large flow loss in centrifugal compressors, and improved compressor performance by modifying the impeller thickness and blade angle.
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