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Research Papers

Advanced Nonaxisymmetric Endwall Contouring for Axial Compressors by Generating an Aerodynamic Separator—Part II: Experimental and Numerical Cascade Investigation

[+] Author and Article Information
Alexander Hergt1

 German Aerospace Center (DLR), Institute of Propulsion Technology, 51147 Cologne, Germanyalexander.hergt@dlr.de

Christian Dorfner, Wolfgang Steinert, Eberhard Nicke, Heinz-Adolf Schreiber

 German Aerospace Center (DLR), Institute of Propulsion Technology, 51147 Cologne, Germany

1

Corresponding author.

J. Turbomach 133(2), 021027 (Oct 27, 2010) (8 pages) doi:10.1115/1.4001224 History: Received August 05, 2009; Revised September 03, 2009; Published October 27, 2010; Online October 27, 2010

Modern methods for axial compressor design are capable of shaping the blade surfaces in a three-dimensional way. Linking these methods with automated optimization techniques provides a major benefit to the design process. The application of nonaxisymmetric contoured endwalls is considered to be very successful in turbine rotors and vanes. Concerning axial compressors, nonaxisymmetric endwalls are still a field of research. This two-part paper presents the recent development of a novel endwall design. A vortex created by a nonaxisymmetric endwall groove acts as an aerodynamic separator, preventing the passage vortex from interacting with the suction side boundary layer. This major impact on the secondary flow results in a significant loss reduction by means of load redistribution, reduction in recirculation areas, and suppressed corner separation. Part I of this paper deals with the endwall design and its compressor application. The resulting flow phenomena and physics are described and analyzed in detail. The second paper presents the detailed experimental and numerical investigation of the developed endwall groove. The measurements carried out at the transonic cascade wind tunnel of DLR in Cologne, demonstrated a considerable influence on the cascade performance. A loss reduction and redistribution of the cascade loading were achieved at the aerodynamic design point, as well as near the stall condition of the cascade. This behavior is well predicted by the numerical simulation. The combined analysis of experimental and numerical flow patterns allows a detailed interpretation and description of the resulting flow phenomena. In this context, high fidelity 3D-Reynolds-averaged Navier–Stokes flow simulations are required to analyze the complex blade and endwall boundary layer interaction.

Copyright © 2011 by American Society of Mechanical Engineers
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References

Figures

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Figure 4

Cascade parameters and pressure taps location on the contoured endwall

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Figure 5

Cascade parameters and MP at inlet and exit

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Figure 6

Oil-flow visualization on endwall (top) and blade suction side (bottom), datum cascade, OP1 at M1=0.69

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Figure 7

Oil-flow visualization on endwall (top) and blade suction side (bottom), CEW cascade, OP1 at M1=0.69

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Figure 8

Stream lines within endwall boundary layer—deflection of endwall cross flow by the aerodynamic separator, OP1

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Figure 9

Simulated secondary flow vectors in x-plane at x/cax=0.47, datum cascade (top), and CEW cascade (bottom); OP1 at M1=0.69

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Figure 10

Total pressure loss distribution at MP2, datum cascade OP1 at M1=0.69, i=0

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Figure 17

Measured and calculated static pressure ratio, OP1 at M1=0.69

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Figure 18

Measured and calculated static pressure ratio, OP2 at M1=0.69

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Figure 19

Measured and calculated outflow angle, OP1 at M1=0.69

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Figure 1

Profile (top) and measured Mach number distribution at midspan of the datum cascade, M1=0.69

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Figure 2

Cascade with nonaxisymmetric endwall contouring

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Figure 3

Cross section of the DLR transonic cascade wind tunnel

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Figure 12

Measured (top) and calculated (bottom) spanwise loss distribution, OP1 at M1=0.69

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Figure 13

Total pressure loss distribution at MP2, datum cascade OP2 at M1=0.69, i=+2

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Figure 14

Total pressure loss distribution at MP2, CEW cascade OP2 at M1=0.69, i=+2.5

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Figure 15

Measured (top) and calculated (bottom) spanwise loss distribution, OP2 at M1=0.69

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Figure 16

Oil-flow pattern on blade suction side, datum, and CEW cascade; OP2 at M1=0.69

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Figure 20

Measured and calculated outflow angle, OP2 at M1=0.69

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Figure 11

Total pressure loss distribution at MP2, CEW cascade OP1 at M1=0.69, i=0

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