The influence of inlet flow distortion on the performance of a centrifugalcompressor and the development of an improved inlet using numerical simulations

The performance of centrifugal compressors can be seriously affected by inl et flow distortions due to the unsatisfactory nature of the inlet configura tion and the resulting inlet flow structure. Experimental tests have been c arried out for the comparison of centrifugal compressor stage efficiency wi th two different inlet configurations, one of which is straight with consta nt cross-sectional area and the other a 90 degrees curved pipe with nozzle shape. The comparative test results indicated significant compressor stage performance difference between the two different inlet configurations and t he details are discussed to understand the performance behaviour of the com pressor exposed to the distorted flow from the bend inlet configuration. Th e experimental investigation motivated the need for a new inlet design as w ell as a clear picture of the detailed flow field in the existing inlet des ign using numerical simulations. Two design approaches are reported in this paper, one of which is the location of vanes and the other the length of t he curvature radius. For a more effective design method, a generalized form ula is developed for the optimum position and number of vanes in such a way that each divided flow passage with vanes shares the same pressure gradien t in radial direction. Numerical simulation results are presented and discu ssed in terms of mass-averaged parameters and flow structures, based on the comparison of flow properties at the pipe exit cross-sectional area of eac h design. Finally, new designs of different inlet systems are proposed to r educe the secondary flow and to provide flow as uniform as possible for a c ompressor.