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Research Papers

Influencing Parameters of Tip Blowing Interacting With Rotor Tip Flow

[+] Author and Article Information
Cyril Guinet, Volker Gümmer

Institute for Turbomachinery and
Flight Propulsion,
Technische Universität München,
Boltzmannstr. 15,
Garching 85748, Germany

André Inzenhofer

Institute for Turbomachinery and
Flight Propulsion,
Technische Universität München,
Boltzmannstr. 15,
Garching 85748, Germany
e-mail: a.inzenhofer@tum.de

1Corresponding author.

Contributed by the International Gas Turbine Institute (IGTI) of ASME for publication in the JOURNAL OF TURBOMACHINERY. Manuscript received May 26, 2016; final manuscript received July 26, 2016; published online October 26, 2016. Editor: Kenneth Hall.

J. Turbomach 139(2), 021010 (Oct 26, 2016) (10 pages) Paper No: TURBO-16-1111; doi: 10.1115/1.4034699 History: Received May 26, 2016; Revised July 26, 2016

The design space of axial-flow compressors is restricted by stability issues. Different axial-type casing treatments (CTs) have shown their ability to enhance compressor stability and to influence efficiency. Casing treatments have proven to be effective, but there still is need for more detailed investigations and gain of understanding for the underlying flow mechanism. Casing treatments are known to have a multitude of effects on the near-casing 3D flow field. For transonic compressor rotors, these are more complex, as super- and subsonic flow regions alternate while interacting with the casing treatment. To derive design rules, it is important to quantify the influence of the casing treatment on the different tip flow phenomena. Designing a casing treatment in a way that it antagonizes only the deteriorating secondary flow effects can be seen as a method to enhance stability while increasing efficiency. The numerical studies are carried out on a tip-critical rotor of a 1.5-stage transonic axial compressor. The examined recirculating tip blowing casing treatment (TBCT) consists of a recirculating channel with an air off-take above the rotor and an injection nozzle in front of the rotor. The design and functioning of the casing treatment are influenced by various parameters. A variation of the geometry of the tip blowing, more specifically the nozzle aspect ratio, the axial position, or the tangential orientation of the injection port, was carried out to identify key levers. The tip blowing casing treatment is defined as a parameterized geometric model and is automatically meshed. A sensitivity analysis of the respective design parameters of the tip blowing is carried out on a single rotor row. Their impact on overall efficiency and their ability to improve stall margin are evaluated. The study is carried out using unsteady Reynolds-averaged Navier–Stokes (URANS) simulations.

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References

Figures

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Fig. 1

Numerical setup of 1.5-stage research compressor

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Fig. 2

Schematic illustration of the TBCT

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Fig. 3

Definition of co- and counter-swirl injection

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Fig. 4

Shock vortex interaction (a) comparing the vortex core trajectory for PE and NSSC and the equivalent shock front. Surfaces perpendicular to the blade chord showing relative total pressure for PE (b) and NSSC (c) of time-averaged solution.

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Fig. 5

Meridional surface with axial velocity vectors (TACMA) at NSSC

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Fig. 6

Speed line comparing SC and reference TBCT for normalized total pressure ratio (a) and normalized polytropic efficiency (b) plotted over normalized corrected mass flow using SC DP as reference

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Fig. 7

Delta of total pressure (TACMA) compared to SC configuration in the tip near region evaluated at a station at leading edge; red-dotted line represents the tip rotor tip clearance

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Fig. 8

Delta of relative total pressure (TACMA) compared to SC configuration in the tip near region evaluated at a station at leading edge for an altering nozzle height; operating points: (a) PE and (b) NSSC

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Fig. 9

Delta in polytropic efficiency relative to SC normalized by the SC polytropic efficiency in the DP depending on the nozzle height for different operating points

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Fig. 10

Meridional surface with delta of relative total pressure (TACMA) at NSSC with schematic TBCT in black 100% and blue 400%

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Fig. 11

Schematic velocity triangles for an axial injection (a), an optimal counter-swirl injection (b), an exaggerated counter-swirl injection (c), and a co-swirl injection (d)

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Fig. 12

Delta of relative total pressure (TACMA) compared to SC configuration in the tip near region evaluated at a station at leading edge for an altering injection angle (bold = PE and dotted = NSSC)

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Fig. 13

Normalized total pressure characteristic plotted over normalized corrected exit mass flow for different TBCT tangential injection angles, numerical stall point highlighted in red

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Fig. 14

Delta in polytropic efficiency relative to SC normalized by the SC polytropic efficiency in the DP depending on the TBCT tangential injection angle for different operating points

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Fig. 15

Surge margin depending on the injection angle at the TBCT nozzle

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Fig. 16

Delta in polytropic efficiency relative to SC normalized by the SC polytropic efficiency in the DP depending on the axial distance between nozzle and blade leading edge for different operating points

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Fig. 17

Delta of meridional mass flow density relative to SC for the two analyzed extrema of axial distance between injection nozzle and blade leading edge

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Fig. 18

Delta of relative total pressure (TACMA) compared to SC configuration in the tip near region evaluated at a station at leading edge for an altering axial distance between nozzle and blade leading edge at NSSC

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