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Research Papers

Unsteady Interactions Between Axial Turbine and Nonaxisymmetric Exhaust Hood Under Different Operational Conditions

[+] Author and Article Information
Jing-Lun Fu

Institute of Engineering Thermophysics, Chinese Academy of Sciences, Beijing 100190, Chinafujl@mail.etp.ac.cn

Jian-Jun Liu

Institute of Engineering Thermophysics, Chinese Academy of Sciences, Beijing 100190, Chinajjl@mail.etp.ac.cn

Si-Jing Zhou

Institute of Engineering Thermophysics, Chinese Academy of Sciences, Beijing 100190, Chinasjzhou@mail.etp.ac.cn

J. Turbomach 134(4), 041002 (Jul 19, 2011) (11 pages) doi:10.1115/1.4003647 History: Received December 16, 2009; Revised November 11, 2010; Published July 19, 2011; Online July 19, 2011

The exhaust system in condensing steam turbines is used to recover leaving kinetic energy of the last stage turbine, while guiding the flow from turbine to condenser. The flows in the exhaust system and the turbine stage are fully coupled and inherently unsteady. The unsteady flow interactions between the turbine and the exhaust system have a strong impact on the blade loading or blade aerodynamic force. This paper describes the unsteady flow interactions between a single-stage axial turbine and an exhaust system. The experimental and numerical studies on the coupled flow field in the single-stage turbine and the exhaust hood model under different operational conditions have been carried out. Unsteady pressure at the turbine rotor blade, turbine outlet, and exhaust outcasing are measured and compared with the numerical prediction. The details of unsteady flow in the exhaust system with the whole annulus stator and rotor blade rows are simulated by employing the computational fluid dynamics software CFX-5 . Results show that for the investigated turbine-exhaust configuration the influence of the flow field in the exhaust system on the unsteady blade force is much stronger than that of the stator and rotor interaction. The flow pattern in the exhaust system changes with the turbine operational condition, which influences the unsteady flow in the turbine stage further.

Copyright © 2012 by American Society of Mechanical Engineers
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Figures

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Figure 1

Experimental schematic

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Figure 2

Turbine and exhaust hood test section

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Figure 3

Positions of unsteady pressure measurements on the rotor blade surface at 50% span

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Figure 4

(a) Schematic and (b) calibration curve of the fast-response total pressure probe

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Figure 5

Diagram of the computational domain: (I) inlet extension, (II) stator blade row, (III) rotor blade row, (IV) diffuser, and (V) collector

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Figure 6

Computational meshes for the full domain: (a) stator and rotor passages, (b) rotor blade tip, and (c) single-stage turbine and exhaust hood

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Figure 7

Comparison of pressure simulated under different time-steps: (a) unsteady pressure at PL and (b) unsteady pressure at ST

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Figure 8

Computed unsteady pressure at monitor points PL and ST using different time-steps: (a) unsteady pressure at PL and (b) unsteady pressure at ST

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Figure 9

Computed unsteady coefficient of force component Ct for the rotor blade: (a) Ct in time domain and (b) frequency spectrum of Ct

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Figure 10

Comparison of the unsteady pressure at PL: (a) Cp in time domain and (b) frequency spectrum of Cp

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Figure 11

Comparison of the unsteady pressure at PT: (a) Cp in time domain and (b) frequency spectrum of Cp

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Figure 12

Unsteady pressure at SL: (a) Cp in time domain and (b) frequency spectrum of Cp

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Figure 13

Comparison of the unsteady pressure at ST: (a) Cp in time domain and (b) frequency spectrum of Cp

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Figure 14

Measured swirl angle distributions at the stage exit

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Figure 15

Simulated stream traces at the stage exit: (a) Case 1, (b) Case 2, and (c) Case 3

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Figure 16

Simulated distributions of Cp in the circumferential direction downstream the turbine stage at 50% span for different time-steps

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Figure 17

Computed and measured unsteady total pressure downstream the turbine stage at 50% span for Case 1: (a) Ctp in time domain and (b) frequency spectrum of Ctp

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Figure 18

Computed and measured unsteady total pressure downstream the turbine stage at 50% span, θ=−90 deg for Case 2: (a) Ctp in time domain and (b) frequency spectrum of Ctp

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Figure 19

Computed and measured unsteady total pressure downstream the turbine stage at 50% span for Case 3: (a) Ctp in time domain and (b) frequency spectrum of Ctp

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Figure 20

Computed and measured unsteady pressure at collector end-wall C5, θ=−90 deg for Case 1: (a) Cp in time domain and (b) frequency spectrum of Cp

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Figure 21

Computed and measured unsteady pressure at collector end-wall C5, θ=−90 deg for Case 3: (a) Cp in time domain and (b) frequency spectrum of Cp

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Figure 22

Instantaneous Ctp contours in the exhaust hood at the section of θ=0° for Case 1: (a) t/T=0, (b) t/T=0.25, (c) t/T=0.50, and (d) t/T=0.75

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Figure 23

Instantaneous Ctp contours in the exhaust hood at the section of θ=0° for Case 3: (a) t/T=0, (b) t/T=0.25, (c) t/T=0.50, and (d) t/T=0.75

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Figure 24

Flow interactions between turbine and exhaust hood

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