Investigation On The Flow Features And Flowfield Structures Of Centrifugal Compressors

Centrifugal compressors play very important roles in many economic sectors. While the researches on the flow features and flowfield structures for the centrifugal compressors are currently not sufficient to direct the engineering designs or the theoretic analyses due to their complexities and lacking of effective research measures. Based on the previous experimental results in literatures, this dissertation is dedicated to investigate the flow features and flowfield structures of the centrifugal compressors by numerical study and theoretic analysis. The main research contents are as follows:1. The ability of the numerical computation methods in simulating the overall performances and flowfield details of centrifugal compressors has been fully validated by comparisons with the experimental results in the literatures; the accuracy and reliability of the numerical simulation methods have been proved.2. The main secondary flow structures of the unshrouded centrifugal impeller and their mechanisms, distributions and variations have been summarized, respectively. A 3D model for the secondary flow structures of the unshrouded centrifugal impeller is built to provide the direct and detailed understanding of the secondary flow structures.3. The mechanisms for the formation and development of the Jet/Wake structure have been presented, and a 3D model for the formation mechanism of the Jet/Wake structure is provided; the features of the Jet/Wake structure have been summarized in many aspects.4. Variations and features for the secondary flow structures and the Jet/Wake structure of the Krain backswept centrifugal impeller have been studied in details by the means of the numerical simulations and analyses, and the influences of blade backward-curvature on these variations are analyzed in details.5. Coupled computations between the centrifugal compressor and impeller backside cavity have been carried out, the flowfield characteristics and flow mechanisms inside the impeller backside cavity have been studied, analyses and summary for the influences of the impeller backside cavity on the centrifugal compressor performance are provided.