| Centrifugal compressors are usually large energy consumers that their performances are crucial to the national economy. However, the design techniques used by compressor manufacturing factories in our country are still very primitive. The efficiency of the model stage studied in this thesis, originally designed by Nuovo Pignone in the 70s last century, is usually 10% lower than the modern state-of-art products in the current market. The operating cost of the compressor units from Chinese factories may be millions RMB yuans higher per unit annually than the advanced units available in the international market. It is high time for our factories to improve the compressor design techniques to stay in the competitive market.A numerical analytic system for the centrifugal model stage was developed in this thesis based upon the CFD commercial software Fine/Turbine. Detailed flow field information with the main flow features inside the through-flow passages were obtained and studied. Main problems affecting the efficiency of the stage were analyzed carefully. Various approaches for the modification of the stage geometry, including the diffuser, the curved duct and the return channel were explored numerically. The final results indicate that the stage efficiency has been increased by more than 3% with a satisfactory improvement of the flow structure inside the stage. Experimental studies of the model stage were also carried out to verify the numerical calculation. The analytic system developed in this thesis is a powerful tool in the analysis of the flow inside the centrifugal model stage. It can be used in engineering design process to improve the performance of the machine significantly. |
