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Research Papers

Experimental Investigation of Purge Flow Effects on a High Pressure Turbine Stage

[+] Author and Article Information
K. Regina

Laboratory for Energy Conversion,
Department of Mechanical
and Process Engineering,
ETH Zurich,
Sonneggstrasse 3,
Zurich CH-8092, Switzerland
e-mail: regina@lec.mavt.ethz.ch

A. I. Kalfas

Department of Mechanical Engineering,
Aristotle University of Thessaloniki,
Thessaloniki GR-54124, Greece
e-mail: akalfas@auth.gr

R. S. Abhari

Laboratory for Energy Conversion,
Department of Mechanical
and Process Engineering,
ETH Zurich,
Sonneggstrasse 3,
Zurich CH-8092, Switzerland
e-mail: abhari@lec.mavt.ethz.ch

1Corresponding author.

Contributed by the International Gas Turbine Institute (IGTI) of ASME for publication in the JOURNAL OF TURBOMACHINERY. Manuscript received August 6, 2014; final manuscript received August 14, 2014; published online October 28, 2014. Editor: Ronald Bunker.

J. Turbomach 137(4), 041006 (Oct 28, 2014) (8 pages) Paper No: TURBO-14-1197; doi: 10.1115/1.4028432 History: Received August 06, 2014; Revised August 14, 2014

In the present paper, an experimental investigation of the effects of rim seal purge flow on the performance of a highly loaded axial turbine stage is presented. The test configuration consists of a one-and-a-half stage, unshrouded, turbine, with a blading representative of high pressure (HP) gas turbines. Efficiency measurements for various purge flow injection levels have been carried out with pneumatic probes at the exit of the rotor and show a reduction of isentropic total-to-total efficiency of 0.8% per percent of injected mass flow. For three purge flow conditions, the unsteady aerodynamic flow field at rotor inlet and rotor exit has been measured with the in-house developed fast response aerodynamic probe (FRAP). The time-resolved data show the unsteady interaction of the purge flow with the secondary flows of the main flow and the impact on the radial displacement of the rotor hub passage vortex (HPV). Steady measurements at off-design conditions show the impact of the rotor incidence and of the stage flow factor on the resulting stage efficiency and the radial displacement of the rotor HPV. A comparison of the effect of purge flow and of the off-design conditions on the rotor incidence and stage flow factor shows that the detrimental effect of the purge flow on the stage efficiency caused by the radial displacement of the rotor HPV is dominated by the increase of stage flow factor in the hub region rather than by the increase of negative rotor incidence.

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References

Figures

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Fig. 1

Tested rotor geometry isometric view (left) and profile at 6% span (right)

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Fig. 2

Schematics of the purge flow path [16] (not to scale)

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Fig. 3

Time-averaged rms of p1′ (Pa) in stationary FOR at plane R in (a) IR1 = −0.1% and (b) IR3 = 1.2%

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Fig. 4

Time-averaged and circumferentially mass averaged rms of p1' (Pa) at plane R in

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Fig. 5

Time-resolved rms of p1' (Pa) at 6% span in stationary FOR at plane R in (a) IR1 = −0.1% and (b) IR3 = 1.2%

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Fig. 6

Time-averaged and circumferentially mass averaged relative flow yaw angle (deg) at plane R in

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Fig. 7

Time-resolved relative flow yaw angle (deg) at 6% span in stationary FOR at plane R in (a) IR1 = −0.1% and (b) IR3 = 1.2%

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Fig. 8

Time-averaged normalized relative total pressure in rotating FOR at plane R ex (a) IR1 = −0.1% and (b) IR3 = 1.2%

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Fig. 9

Time-resolved rms of p1′ (Pa) in stationary FOR at plane R ex for IR3, locations where the interaction with the NGV 1 secondary flow features is (a) low and (b) high

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Fig. 10

Time-averaged and circumferentially mass averaged isentropic total-to-total stage efficiency at plane R ex

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Fig. 11

Sensitivity of the isentropic total-to-total stage efficiency toward the IR

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Fig. 12

Time-averaged and circumferentially mass averaged isentropic total-to-total stage efficiency at plane R ex

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Fig. 13

Time-averaged and circumferentially mass averaged relative flow yaw angle (deg) at plane R ex

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Fig. 14

Time-averaged and circumferentially mass averaged flow coefficient (a) due to variation of purge flow and (b) due to variation of overall operating point

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