<p>In the present paper, three transonic centrifugal compressor impellers with same design volume flow coefficient (0.185) and same design Machine Mach number (Ma<sub>u2,des</sub>=1.1) are numerically analyzed to investigate the reasons for different measured &nbsp;impeller operational range in IGV (Inlet Guide Vane)-off-design. All three impellers have been numerically optimized and analyzed with means of steady state RANS (Reynolds Averaged Navier Stokes)-CFD (Computational Fluid Dynamics) and have been measured on a test rig of medium size. Two impellers feature a ruling surface blade, the third impeller comprises a fully three-dimensional geometry with bow, and barreled leading edge sweep. Based on the two impellers with full blade design, a &nbsp;fourth impeller is designed to combine the relevant geometric features of the afore mentioned three impellers. The different inducer design and blade geometry result in different span-wise incidence loss characteristics and impeller diffusion at GV-design and off-design operation. In order to gain confidence into the CFD-prediction of the inducer flow, the off-design IGV-exit flow properties are validated against detailed three-hole probe and static pressure tap measurements. Additional focus for the numerical analysis is set on the quantification of the primary flow deviation, impeller secondary flow data and integral and stream-wise generated blockage. Based on the span-wise analysis, integral correlations for diffusion and incidence loss characteristics are derived from CFD-results to feed a modified TEIS (Two Element in Series) and “Two-Zone”-model for IGV-off-design operation. Taking IGV-pre-whirl with a symmetric two-dimensional IGV-airfoil-design into account, the off-design overall stage characteristics can be trimmed to a) provoke improved operational range towards IGV co-rotated swirl, or b) improve peak efficiency operation. For IGV-setting angles up to 45 degree, 0D-,1D-, and 3D-CFD-calculation can well predict the measured work-input within reasonable agreement. Based on CFD and experimental data, the hypothesis of potential correlation between impeller diffusion and secondary flux data is proved for.</p>

On the Correlation Between Span-Wise Inducer Incidence and Impeller Diffusion for Ruled Surface and Barreled Sweep-Bow Impeller Design at Igv-Off-Design

Paper Proceedings: https://asmedigitalcollection.asme.org/GT/GT2021/volume/84898

Turbo Expo 2021

Supporting the need among researchers worldwide for additional online and multimedia content, ASME now offers the ASME Conference Video Collection. This platform will collect and provide long-term access to conference presentation videos, encompassing all technology areas within ASME's technical conference and events program. About 30,000-40,000 engineers across all mechanical engineering and related disciplines participate in ASME conferences each year. This includes authors of approximately 6,000 to 8,000 technical papers published by ASME, the majority of whom also submit video presentations for our virtual conferences. The video collection will be available as an add-on to existing product packages or as a separate subscription.