Research Papers

Numerical and Experimental Comparison of a Tandem and Single Vane Deswirler Used in an Aero Engine Centrifugal Compressor

[+] Author and Article Information
Peter Jeschke

Institute of Jet Propulsion and Turbomachinery,
RWTH Aachen University,
Templergraben 55,
Aachen 52062, Germany
e-mail: jeschke@ist.rwth-aachen.de

Caitlin Smythe

GE Aviation,
1000 Western Avenue MD47410,
Lynn, MA 01910
e-mail: caitlin.smythe@ge.com

Except for some small areas in the transonic inlet of the diffuser.

For the presented investigation the shroud pressure build-up is not available for the SNG case.

Although the averaging method is not conservative, this method serves the purpose of visualizing the weak areas well, due to the fact that the flow field is not weighted.

1Corresponding author.

Contributed by the International Gas Turbine Institute (IGTI) of ASME for publication in the Journal of Turbomachinery. Manuscript received May 3, 2013; final manuscript received June 20, 2013; published online September 26, 2013. Editor: Ronald Bunker.

J. Turbomach 136(4), 041005 (Sep 26, 2013) (10 pages) Paper No: TURBO-13-1067; doi: 10.1115/1.4024891 History: Received May 03, 2013; Revised June 20, 2013

The present work is part of the research project at the Institute of Jet Propulsion and Turbomachinery at the RWTH Aachen University in collaboration with GE Aviation. The subject is the numerical and experimental analysis of two blading strategies used in the diffusion system of an aero engine centrifugal compressor. The transonic centrifugal compressor investigated contains a close-coupled impeller and passage diffuser, followed by a deswirler system. The deswirler redirects the flow towards the combustion chamber, while decreasing swirl and recovering pressure. It is characterized by a high aerodynamic loading, due to a moderate inlet Mach number of 0.35, in combination with a required flow redirection of 70 deg in circumferential and 135 deg in meridional direction. For this purpose, two different blading strategies are investigated, both retaining the same meridional flow path and integral chord length. The first design is a tandem configuration with 30 vanes in the first row and 60 vanes in the second row. In principal, this approach benefits from the small wetted surface, the short and thereby stable boundary layers as well as the positive blade interaction due to the close alignment. The second design contains one row of 75 vanes. The higher solidity is needed to compensate for the longer boundary layers. The two deswirlers investigated are compared to a less compact baseline deswirler with simple prismatic vanes. Experimental and numerical data shows that both new configurations have very similar stage efficiency. The single row design shows a higher static pressure recovery, resulting in a +0.2%-points total-to-static isentropic efficiency increase compared to the tandem design. Detailed flow analysis in the deswirler system shows different characteristics in terms of losses, loss mechanisms and pressure build-up. Due to the required high turning, both designs suffer from flow separation. Nevertheless, the single row design shows its robustness under the impact of 3D flow, whereas the tandem suffers from end wall induced losses. The results show that the classical mechanisms making a tandem favorable for high flow turning in 2D flow are counteracted by 3D flow mechanisms caused by the spanwise pressure gradient. The low aspect ratio even increases the effect of 3D end wall mechanisms. These results, combined with a higher manufacturing effort, show that a tandem configuration is not necessarily the superior design for highly 3D flow conditions.

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Fig. 1

3D view of the three deswirler configurations

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Fig. 2

Cross-sectional view of the test rig

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Fig. 3

3D view of the CFD domain of the centrifugal stage

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Fig. 4

Schematical view of the GE-centrifugal stage

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Fig. 5

ωdiff,norm and Cpdiff,norm over the corrected mass flow at the diffuser inlet calculated between plane 4M and 7M shown in Fig. 4

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Fig. 6

Experimental and numerical diffuser meanline pressure buildup

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Fig. 7

Blade-to-blade loading at 50% span

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Fig. 8

Hub and shroud loading at the centerline in between the deswirler blades

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Fig. 9

Flux-averaged streamwise development of ωnorm

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Fig. 10

Flux-averaged streamwise development of Cpnorm

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Fig. 11

Flux-averaged streamwise development of the flow-angle α

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Fig. 12

Entropy distribution in the TND deswirler

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Fig. 13

Entropy distribution in the SNG deswirler

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Fig. 14

Sources for the 3D flow within the TND deswirler




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