Flow Analysis And Optimization Of The Centrifugal Model Stage With Small Flow Coefficient

Centrifugal compressors are widely used in aeronautics, power and energy, chemical metallurgy-and many other industries for higher stage -pressure ratio and superiors manufacturing technique. The model stage studied in this thesis was designed by Nuovo Pignone in the 70s last century. The efficiency of such a model stage is usually 10% lower than the modern state-of-art products in current market and thus at a very disadvantage position in the competitive market, as the design method is out-of-date now.Based on the CFD software NUMECA, a numerical analytic system for the centrifugal model stage was developed and the detailed flow field with the main flow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 impeller, the diffuser, the curved duct and the return channel were explored numerically. The final results indicate that the stage efficiency has been increased by 6.6% with a satisfactory improvement of the flow structure inside the stage. Vaned diffuser can improve the efficiency of the model stage effectively, although may affect the off-design performance slightly.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.