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Journal of Turbomachinery | Volume 131 | Issue 4 | Research Paper
Research Papers

Effect of Unsteadiness on the Performance of a Transonic Centrifugal Compressor Stage

[+] Author and Article Information
Isabelle Trébinjac, Pascale Kulisa, Nicolas Bulot

Laboratoire de Mécanique des Fluides et d’Acoustique, UMR CNRS 5509, Ecole Centrale de Lyon, UCBLyon I, INSA 36 Avenue Guy de Collongue, 69134 Ecully Cedex, France

Nicolas Rochuon

TURBOMECA, Groupe SAFRAN, 64511 Bordes, France

J. Turbomach 131(4), 041011 (Jul 02, 2009) (9 pages) doi:10.1115/1.3070575 History: Received August 21, 2008; Revised September 10, 2008; Published July 02, 2009
Article
References
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Citing Articles

Numerical and experimental investigations were conducted in a transonic centrifugal compressor stage composed of a backswept splittered unshrouded impeller and a vaned diffuser. The characteristic curves of the compressor stage resulting from the unsteady simulations and the experiments show a good agreement over the whole operating range. On the contrary, the total pressure ratio resulting from the steady simulations is clearly overestimated. A detailed analysis of the flow field at design operating point led to identify the physical mechanisms involved in the blade row interaction that underlie the observed shift in performance. Attention was focused on the deformation in shape of the vane bow shock wave due its interaction with the jet and wake flow structure emerging from the impeller. An analytical model is proposed to quantify the time-averaged effects of the associated entropy increase. The model is based on the calculation of the losses across a shock wave at various inlet Mach numbers corresponding to the moving of the jet and wake flow in front of the shock wave. The model was applied to the compressor stage performance calculated with the steady simulations. The resulting curve of the overall pressure ratio as a function of the mass flow is clearly shifted toward the unsteady results. The model, in particular, enhances the prediction of the choked mass flow.
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Copyright © 2009 by American Society of Mechanical Engineers
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References

1
Krain, H., 1981, “A Study on Centrifugal Impeller and Diffuser Flow,” ASME J. Eng. Power, 103 , pp. 688–697.
2
Inoue, M., and Cumpsty, N. A., 1984, “Experimental Study of Centrifugal Impeller Discharge Flow in Vaneless and Vaned Diffusers,” ASME J. Eng. Gas Turbines Power, 106 , pp. 455–467.
3
Ziegler, K. U., Gallus, H. E., and Niehuis, R. A., 2003, “A Study on Impeller-Diffuser Interaction—Part I: Influence on the Performance,” ASME J. Turbomach.  [CrossRef], 125 , pp. 173–182.
4
Ziegler, K. U., Gallus, H. E., and Niehuis, R. A., 2003, “A Study on Impeller-Diffuser Interaction—Part II: Detailed Flow Analysis,” ASME J. Turbomach.  [CrossRef], 125 , pp. 183–192.
5
Deniz, S., Greitzer, E. M., and Cumpsty, N. A., 2000, “Effects of Inlet Flow Field Conditions on the Performance of Centrifugal Compressor Diffusers—Part II: Straight-Channel Diffuser,” ASME J. Turbomach.  [CrossRef], 122 , pp. 11–21.
6
Shum, Y. K. P., Tan, C. S., and Cumpsty, N. A., 2000, “Impeller-Diffuser Interaction in a Centrifugal Compressor,” ASME J. Turbomach.  [CrossRef], 122 , pp. 777–786.
7
Krain, H., 2002, “Unsteady Diffuser Flow in a Transonic Centrifugal Compressor,” Int. J. Rotating Mach., 8 , pp. 223–231.
8
Krain, H., and Hah, C., 2003, “Numerical and Experimental Investigation of the Unsteady Flow Field in a Transonic Centrifugal Compressor,” "Proceedings of the International Gas Turbine Congress, IGTC2003", Tokyo, Japan.
9
Rochuon, N., 2007, “Analyse de l’écoulement tridimensionnel instationnaire dans un compresseur centrifuge à fort taux de pression,” Ph.D. thesis, Ecole Centrale de Lyon, Cedex, France.
10
Smith, B. R., 1994, “Prediction of Hypersonic Shock Wave Turbulent Boundary Layer Interactions With the k-l Two-Equation Turbulence Model,” AIAA Paper No. 95–02232.
11
Kulisa, P., and Dano, C., 2006, “Assessment of Linear and Non-Linear Two-Equation Turbulence Models for Aerothermal Turbomachinery Flows,” J. Therm. Sci.  [CrossRef], 15 (1), pp. 14–26.
12
Cambier, L., and Gazaix, M., 2002, “elsA: An Efficient Object-Oriented Solution to CFD Complexity,” 40th AIAA Aerospace Science Meeting and Exhibit , Reno, NV.
13
Martinelli, L., 1987, “Calculation of Viscous Flows With a Multigrid Method,” Ph.D. thesis, Princeton University, Princeton, NJ.
14
Jameson, A., 1985, “Multigrid Algorithms for Compressible Flow Calculations,” "Lecture Notes in Mathematics", Vol. 1228 , Springer-Verlag, Berlin.
15
Bulot, N., and Trébinjac, I., 2007, “Impeller-Diffuser Interaction: Analysis of the Unsteady Flow Structures Based on Their Direction of Propagation,” J. Therm. Sci., 16 (3), pp. 193–202.
16
Gorrell, S. E., Okiishi, T. H., and Copenhaver, W. W., 2002, “Stator-Rotor Interactions in a Transonic Compressor: Part 2—Description of a Loss Producing Mechanism,” ASME Paper No. GT-2002–30495.
17
Rohne, K. H., and Banzhaf, M., 1991, “Investigation of the Flow at the Exit of an Unshrouded Centrifugal Impeller and Comparison With the Classical Jet-Wake Theory,” ASME J. Turbomach.  [CrossRef], 113 , pp. 654–659.

Figures

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+3D sketch of the centrifugal compressor stage
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3D sketch of the centrifugal compressor stage
Figure 1

3D sketch of the centrifugal compressor stage

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+Meridional view of the compressor stage
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Meridional view of the compressor stage
Figure 2

Meridional view of the compressor stage

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+H-C-O topology of the mesh
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H-C-O topology of the mesh
Figure 3

H-C-O topology of the mesh

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+Pressure ratio of the compressor stage
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Pressure ratio of the compressor stage
Figure 4

Pressure ratio of the compressor stage

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+Reduced temperature rise
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Reduced temperature rise
Figure 5

Reduced temperature rise

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+Level of unsteadiness through the impeller (a) and through the vaned diffuser (b)
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Level of unsteadiness through the impeller (a) and through the vaned diffuser (b)
Figure 6

Level of unsteadiness through the impeller (a) and through the vaned diffuser (b)

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+Reduced meridional velocity at section E (m∗=0.63)
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Reduced meridional velocity at section E (m∗=0.63)
Figure 7

Reduced meridional velocity at section E (m∗=0.63)

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+Reduced tangential velocity at section E (m∗=0.63)
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Reduced tangential velocity at section E (m∗=0.63)
Figure 8

Reduced tangential velocity at section E (m∗=0.63)

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+Purely unsteady relative velocity at mid inter-row gap and 70% section height, over a stator pitch and a rotor time-period
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Purely unsteady relative velocity at mid inter-row gap and 70% section height, over a stator pitch and a rotor time-period
Figure 9

Purely unsteady relative velocity at mid inter-row gap and 70% section height, over a stator pitch and a rotor time-period

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+Meridional evolution of entropy
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Meridional evolution of entropy
Figure 10

Meridional evolution of entropy

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+Absolute Mach number contours, at 50% section height
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Absolute Mach number contours, at 50% section height
Figure 11

Absolute Mach number contours, at 50% section height

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+Absolute Mach number, at 50% height
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Absolute Mach number, at 50% height
Figure 12

Absolute Mach number, at 50% height

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+Absolute normal Mach number, close to impeller exit
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Absolute normal Mach number, close to impeller exit
Figure 13

Absolute normal Mach number, close to impeller exit

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+Corrected pressure ratio of the compressor stage
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Corrected pressure ratio of the compressor stage
Figure 14

Corrected pressure ratio of the compressor stage

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