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Research Papers

Experimental and Numerical Verification of an Optimization of a Fast Rotating High-Performance Radial Compressor Impeller

[+] Author and Article Information
M. Elfert

Institute of Propulsion Technology,
German Aerospace Center DLR,
Linder Hoehe,
Cologne 51147, Germany
e-mail: martin.elfert@dlr.de

A. Weber, D. Wittrock, A. Peters, C. Voss, E. Nicke

Institute of Propulsion Technology,
German Aerospace Center DLR,
Linder Hoehe,
Cologne 51147, Germany

Contributed by the International Gas Turbine Institute (IGTI) of ASME for publication in the JOURNAL OF TURBOMACHINERY. Manuscript received January 24, 2017; final manuscript received February 22, 2017; published online May 9, 2017. Editor: Kenneth Hall.

J. Turbomach 139(10), 101007 (May 09, 2017) (9 pages) Paper No: TURBO-17-1015; doi: 10.1115/1.4036357 History: Received January 24, 2017; Revised February 22, 2017

An optimization has been performed on a well-proven radial compressor design known as the SRV4 impeller (the Krain impeller), which has been extensively tested in the past, using the autoopti tool developed at DLR's Institute of Propulsion Technology. This tool has shown its capability in several tasks, mainly for axial compressor and fan design as well as for turbine design. The optimization package autoopti was applied to the redesign and optimization of a radial compressor stage with a vaneless diffusor. This optimization was performed for the SRV4 compressor geometry without fillets using a relatively coarse structured mesh in combination with wall functions. The impeller geometry deduced by the optimization had to be slightly modified due to manufacturing constraints. In order to filter out the improvements of the new so-called SRV5 radial compressor design, two work packages were conducted: The first one was the manufacturing of the new impeller and its installation on a test rig to investigate the complex flow inside the machine. The aim was, first of all, the evaluation of a classical performance map and the efficiency chart achieved by the new compressor design. The efficiencies realized in the performance chart were enhanced by nearly 1.5%. A 5% higher maximum mass flow rate was measured in agreement with the Reynolds-averaged Navier–Stokes (RANS) simulations during the design process. The second work package comprises the computational fluid dynamics (CFD) analysis. The numerical investigations were conducted with the exact geometries of both the baseline SRV4 as well as the optimized SRV5 impeller including the exact fillet geometries. To enhance the prediction accuracy of pressure ratio and impeller efficiency, the geometries were discretized by high-resolution meshes of approximately 5 × 106 cells. For the blade walls as well as for the hub region, the mesh resolution allows a low-Reynolds approach in order to get high-quality results. The comparison of the numerical predictions and the experimental results shows a very good agreement and confirms the improvement of the compressor performance using the optimization tool autoopti.

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References

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Figures

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Fig. 1

Meridional flow path and geometry limits of SRV4 (basic) and SRV5 (optimized)

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Fig. 2

Geometries for basic impeller SRV4 (left) and new impeller SRV5 (right) with detailed view

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Fig. 3

Impeller performance map for total pressure ratio: Comparison for simplified geometries (no hub fillets, CFD). Design speed: 50,000 min−1. Reference planes 2–3 (see Fig. 8).

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Fig. 4

DLR's new SRV5 impeller with its characteristic S-shaped leading edges mounted on the rig

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Fig. 5

Test section with instrumentation and computational domain

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Fig. 6

SRV5: Basic CH-type topology at tip. Clearance gaps: H-type blocks.

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Fig. 7

CH-type grid structure at impeller trailing edge plane

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Fig. 8

Zonal area in unvaned diffusor part. Definition of reference planes 1–4.

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Fig. 9

SRV5: Validation of performance maps at design wheel speed (50,000 min−1)

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Fig. 10

SRV4: Validation of performance maps at design wheel speed (50,000 min−1)

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Fig. 11

SRV5: Static pressure development along the shroud at peak efficiency and design wheel speed (50,000 min−1)

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Fig. 12

Comparison of calculated performance maps for SRV4 (left) and SRV5 (right) at design wheel speed (50,000 min−1)

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Fig. 13

SRV5: Mach number distribution at 90% of relative channel height. Near choke at design wheel speed (50,000 min−1), Fig. 12.

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Fig. 14

SRV4: Mach number distribution at 90% of relative channel height. Near choke at design wheel speed (50,000 min−1), Fig. 12.

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Fig. 15

SRV5: Mach number distribution at 90% of relative channel height. Peak efficiency at design wheel speed (50,000 min−1), Fig. 12.

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Fig. 16

SRV4: Mach number distribution at 90% of relative channel height. Peak efficiency at design wheel speed (50,000 min−1), Fig. 12.

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Fig. 17

Isentropic Mach number distribution at 90% of span (peak efficiency) at design wheel speed (50,000 min−1). SRV4: dashed lines and SRV5: solid lines.

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Fig. 18

Spanwise traverse planes I: near LE and II: 10 mm downstream of the TE

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Fig. 19

Spanwise circumferentially averaged velocity distribution near leading edge and trailing edge

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Fig. 20

SRV5: Mach number distribution on streamwise S3 cuts (peak efficiency) at design wheel speed (50,000 min−1)

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Fig. 21

SRV4: Mach number distribution on streamwise S3 cuts (peak efficiency) at design wheel speed (50,000 min−1)

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