1. Date of download: 6/1/2016 Copyright © ASME. All rights reserved. From: On the Combined Effect on Operating Range of Adjustable Inlet Guide Vanes and Variable Speed in Process Multistage Centrifugal Compressors J. Eng. Gas Turbines Power. 2014;136(8):082601-082601-10. doi:10.1115/1.4026621 The sign of swirl is positive (in both absolute and relative frames) if the tangential component is oriented as the blade speed Figure Legend:

2. Date of download: 6/1/2016 Copyright © ASME. All rights reserved. From: On the Combined Effect on Operating Range of Adjustable Inlet Guide Vanes and Variable Speed in Process Multistage Centrifugal Compressors J. Eng. Gas Turbines Power. 2014;136(8):082601-082601-10. doi:10.1115/1.4026621 Single stage equipped with IGVs. Contours of polytropic efficiency in the Hp-Q plane are reported for four different IGVs openings: 60 deg (almost closed IGVs), 40 deg, 20 deg, and −15 deg (fully open IGVs). Figure Legend:

3. Date of download: 6/1/2016 Copyright © ASME. All rights reserved. From: On the Combined Effect on Operating Range of Adjustable Inlet Guide Vanes and Variable Speed in Process Multistage Centrifugal Compressors J. Eng. Gas Turbines Power. 2014;136(8):082601-082601-10. doi:10.1115/1.4026621 Multistage compressor equipped with IGVs. Contours of polytropic efficiency in the Hp-Q plane are reported for four different IGVs openings: 60 deg (almost closed IGVs), 40 deg, 20 deg, and −15 deg (fully open IGVs). Figure Legend:

4. Date of download: 6/1/2016 Copyright © ASME. All rights reserved. From: On the Combined Effect on Operating Range of Adjustable Inlet Guide Vanes and Variable Speed in Process Multistage Centrifugal Compressors J. Eng. Gas Turbines Power. 2014;136(8):082601-082601-10. doi:10.1115/1.4026621 Maps with and without IGVs for a compressor where the first stage is taken at ϕ / ϕ * = 0.85 and the unregulated part is taken at ϕ / ϕ * = 1. The map on the background corresponds to the current selection (first stage at ϕ / ϕ * = 0.85) at IGV = 0 deg. Figure Legend:

5. Date of download: 6/1/2016 Copyright © ASME. All rights reserved. From: On the Combined Effect on Operating Range of Adjustable Inlet Guide Vanes and Variable Speed in Process Multistage Centrifugal Compressors J. Eng. Gas Turbines Power. 2014;136(8):082601-082601-10. doi:10.1115/1.4026621 Maps with and without IGVs for a compressor where the first stage is taken at ϕ / ϕ * = 0.85 and the unregulated part is taken at ϕ / ϕ * = 1. The map on the background corresponds to the original selection (all stages at ϕ / ϕ * = 1) at IGV = 0 deg. Figure Legend:

6. Date of download: 6/1/2016 Copyright © ASME. All rights reserved. From: On the Combined Effect on Operating Range of Adjustable Inlet Guide Vanes and Variable Speed in Process Multistage Centrifugal Compressors J. Eng. Gas Turbines Power. 2014;136(8):082601-082601-10. doi:10.1115/1.4026621 Two-stage compressor with MU = 0.85 for the first stage Figure Legend:

7. Date of download: 6/1/2016 Copyright © ASME. All rights reserved. From: On the Combined Effect on Operating Range of Adjustable Inlet Guide Vanes and Variable Speed in Process Multistage Centrifugal Compressors J. Eng. Gas Turbines Power. 2014;136(8):082601-082601-10. doi:10.1115/1.4026621 Efficiency contours at IGV = 40 deg (dashed gray area) superimposed to the same map at IGV = 0 deg Figure Legend:

8. Date of download: 6/1/2016 Copyright © ASME. All rights reserved. From: On the Combined Effect on Operating Range of Adjustable Inlet Guide Vanes and Variable Speed in Process Multistage Centrifugal Compressors J. Eng. Gas Turbines Power. 2014;136(8):082601-082601-10. doi:10.1115/1.4026621 Red-dashed lines (contours of polytropic efficiency). Solid lines: contours of flow coefficient for the stages from the first one to the last one. Figure Legend:

9. Date of download: 6/1/2016 Copyright © ASME. All rights reserved. From: On the Combined Effect on Operating Range of Adjustable Inlet Guide Vanes and Variable Speed in Process Multistage Centrifugal Compressors J. Eng. Gas Turbines Power. 2014;136(8):082601-082601-10. doi:10.1115/1.4026621 Turndown and stability superimposed to line at constant flow coefficient for the first (black) and the last stage (orange) Figure Legend:

10. Date of download: 6/1/2016 Copyright © ASME. All rights reserved. From: On the Combined Effect on Operating Range of Adjustable Inlet Guide Vanes and Variable Speed in Process Multistage Centrifugal Compressors J. Eng. Gas Turbines Power. 2014;136(8):082601-082601-10. doi:10.1115/1.4026621 Plots of ϕ / ϕ * along turndown (top) and stability (bottom) paths for the compressor of Fig. 9 Figure Legend:

11. Date of download: 6/1/2016 Copyright © ASME. All rights reserved. From: On the Combined Effect on Operating Range of Adjustable Inlet Guide Vanes and Variable Speed in Process Multistage Centrifugal Compressors J. Eng. Gas Turbines Power. 2014;136(8):082601-082601-10. doi:10.1115/1.4026621 Contours of flow coefficient for stages 1, 4, and 7 of the seven-stage compressor of Fig. 7 Figure Legend:

12. Date of download: 6/1/2016 Copyright © ASME. All rights reserved. From: On the Combined Effect on Operating Range of Adjustable Inlet Guide Vanes and Variable Speed in Process Multistage Centrifugal Compressors J. Eng. Gas Turbines Power. 2014;136(8):082601-082601-10. doi:10.1115/1.4026621 Relative variations of flow coefficient (top) and polytropic head (bottom) for the each of the seven stages as the IGVs angle goes from 0 deg to 40 deg Figure Legend: