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Research Papers

Numerical Simulation of the Flow Pulsations Origin in Cascades of the Rear Blade Rows in a Gas Turbine Axial Compressor Using Low Calorific Fuel

[+] Author and Article Information
Vaclav Cyrus

 AHT Energetics Ltd., Podnikatelska 550, Prague-Bechovice, Prague 19011, Czech Republiccyrus.aht@iol.cz

Jiri Polansky

 West Bohemia University, Universitni 8, Pilsen 30616polansky@kke.zcu.cz

J. Turbomach 132(3), 031012 (Mar 25, 2010) (11 pages) doi:10.1115/1.3153306 History: Received March 10, 2009; Revised April 17, 2009; Published March 25, 2010; Online March 25, 2010

Fatigue failure of the last three stator rows vanes (S17, EGV1, and EGV2) in the 17 stage gas turbine axial compressor occurred in the power plant where low calorific fuel syngas, was used. Causes of this dangerous phenomenon were flow pulsations with the frequency of 380–400 Hz that were found by the experimental investigation of the duty gas turbine. Mechanism of the flow unsteadiness origin was studied with the help of flow simulations in the 2D stator cascade system. Three numerical experiments were carried out. The first experiment investigated the flow simulation in the stator cascade system with a steady undisturbed inlet flow with increased turbulence intensity. Obtained data did not meet the standards of the actual compressor operations. In the remaining two numerical experiments, a purposely designed rotor cascade was located in front of the stator cascades. Shedding of vortex structures from the cascade profile surfaces at positive incidence angles is responsible for the flow pulsation origin. The interaction of rotor wakes/stator S17 cascade plays an important role in the investigated phenomenon, as follows from CFD data. Aerodynamic loading of both cascades is equal in the second group of numerical experiments. Computed results were in good qualitative agreement with the experimental ones. As the flow in rotor cascade was not separated, owing to the different aerodynamic loading of rotor and stator S17 cascades, the vortices shedding in stator cascade S17 had a significantly higher frequency of f=22002300Hz than in other investigated cases.

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Copyright © 2010 by American Society of Mechanical Engineers
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Figures

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Figure 1

Axial compressor

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Figure 2

Stator vane damage

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Figure 3

Compressor characteristics

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Figure 4

(a) Total pressure in plane 4—P=105 MW and (b) amplitude/frequency characteristic of total pressure in plane 4—P=105 MW

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Figure 5

Cascade system B1 and B2 a=24 mm, b=22 mm

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Figure 6

Instantaneous vorticity patterns—(A)

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Figure 7

Unsteady distribution of S17 vane force—(A)

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Figure 8

(a) Instantaneous vorticity magnitude field—iS17=0 deg, (B1); (b) instantaneous vorticity magnitude field—iS17=4 deg, (B1); and (c) instantaneous vorticity magnitude field—iS17=7 deg, (B1)

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Figure 9

Rotor pitchwise distribution of the time averaged absolute flow angle α1,S17 in the plane behind rotor

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Figure 10

Time dependent distribution of S17 vane force

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Figure 11

(a) Amplitude-frequency characteristics of rotor blades forces—(B1), (b) amplitude-frequency characteristics of stator vanes forces—(B1), (c) amplitude-frequency characteristics of EGV1 forces—(B1), and (d) Amplitude-frequency characteristics of total pressure—(B1)

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Figure 12

Instantaneous vorticity magnitudes field iR=4.7 deg, iS17=5.6 deg, (B2)

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Figure 13

Instantaneous vorticity magnitudes field iR=2.8 deg, iS17=6.8 deg, (B2)

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Figure 14

Amplitude-frequency characteristics of rotor R and S17 blade forces—(B2)

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