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Research Papers

A Parametric Study of the Blade Row Interaction in a High Pressure Turbine Stage

[+] Author and Article Information
G. Persico

Dipartimento di Energia, Politecnico di Milano, Via la Masa 34, Milano 20158, Italygiacomo.persico@polimi.it

P. Gaetani, C. Osnaghi

Dipartimento di Energia, Politecnico di Milano, Via la Masa 34, Milano 20158, Italy

J. Turbomach 131(3), 031006 (Apr 08, 2009) (13 pages) doi:10.1115/1.2987236 History: Received July 18, 2007; Revised April 04, 2008; Published April 08, 2009

An extensive experimental analysis on the subject of the unsteady periodic flow in a high subsonic high pressure (HP) turbine stage has been carried out at the Laboratorio di Fluidodinamica delle Macchine of the Politecnico di Milano (Italy). In this paper the aerodynamic blade row interaction in HP turbines, enforced by increasing the stator and rotor blade loading and by reducing the stator-rotor axial gap, is studied in detail. The time-averaged three-dimensional flowfield in the stator-rotor gap was investigated by means of a conventional five-hole probe for the nominal (0 deg) and highly positive (+22deg) stator incidences. The evolution of the viscous flow structures downstream of the stator is presented to characterize the rotor incoming flow. The blade row interaction was evaluated on the basis of unsteady aerodynamic measurements at the rotor exit, performed with a fast-response aerodynamic pressure probe. Results show a strong dependence of the time-averaged and phase-resolved flowfield and of the stage performance on the stator incidence. The structure of the vortex-blade interaction changes significantly as the magnitude of the rotor-inlet vortices increases, and very different residual traces of the stator secondary flows are found downstream of the rotor. On the contrary, the increase in rotor loading enhances the unsteadiness in the rotor secondary flows but has a little effect on the vortex-vortex interaction. For the large axial gap, a reduction of stator-related effects at the rotor exit is encountered when the stator incidence is increased as a result of the different mixing rate within the cascade gap.

Copyright © 2009 by American Society of Mechanical Engineers
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References

Figures

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Figure 1

LFM axial section meridional cut; TS and TR (referred as TR1) are reported

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Figure 2

Steady stator-exit flowfield. Left to right: Nominal Case, Case 1, Case 0, and Case 3. (a) Y and (b) Ω.

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Figure 3

Radial pitchwise-averaged distributions for the Nominal Case, Case 1, and Case 3. From left to right: total pressure loss (Y), Mach numbers (Mr, Mx, and M), and blade-to-blade flow angle (α).

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Figure 4

Rotor-inlet relative flow. Left to right: Nominal Case, Case 1, Case 2, Case 0, and Case 3. (a) CptR and (b) IR.

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Figure 5

Pitchwise averaged CptR (left) and IR (right) at the rotor inlet in the Nominal, 0, 1, 2, and 3 Cases

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Figure 6

Mean rotor-exit flow (CptR, δ, Cps, and α) in the Nominal Case

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Figure 7

Periodic RMS (CptR and δ) in the Nominal Case

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Figure 8

Instantaneous rotor-exit flowfield in the Nominal Case: CptR (top) and δ (bottom)

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Figure 9

Mean rotor-exit flow (CptR, δ, Cps, and α) for Case 1

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Figure 10

Periodic RMS (CptR and δ) for Case 1

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Figure 11

Instantaneous rotor-exit flowfield for Case 1: CptR (top) and δ (bottom)

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Figure 12

Kinematic vortex transport model applied to Case 1. (a) Transport of hub stator vortices and (b) vortex-vortex interaction.

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Figure 13

Mean rotor-exit flow (CptR, δ, Cps, and α) for Case 2

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Figure 14

Periodic RMS (CptR and δ) for Case 2

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Figure 15

Instantaneous rotor-exit flowfield for Case 2: CptR (top) and δ (bottom)

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Figure 16

Periodic RMS comparison between Case 0 (left) and Case 3 (right)

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Figure 17

Radial pitchwise-averaged distributions of stage efficiency

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