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Research Papers

Aerothermal Impact of the Interaction Between Hub Leakage and Mainstream Flows in Highly-Loaded High Pressure Turbine Blades

[+] Author and Article Information
Ivan Popović

e-mail: ivan.popovic@cantab.net

Howard P. Hodson

Whittle Laboratory,
University of Cambridge,
Cambridge CB3 ODY, UK

Contributed by the International Gas Turbine Institute (IGTI) of ASME for publication in the JOURNAL OF TURBOMACHINERY. Manuscript received April 29, 2012; final manuscript received January 28, 2013; published online September 13, 2013. Editor: David Wisler.

J. Turbomach 135(6), 061014 (Sep 13, 2013) (11 pages) Paper No: TURBO-12-1037; doi: 10.1115/1.4023621 History: Received April 29, 2012; Revised January 28, 2013

This paper describes experimental and numerical investigations of a highly-loaded rotor blade with leakage (purge) flow injection through an upstream overlapping seal. The effects of both leakage mass flow rates and swirl have been studied to examine their effects on the aerothermal performance. As the leakage mass flow rate was increased, the loss generally increased. The increase in the losses was found to be nonlinear with the three distinct regimes of leakage-mainstream interaction being identified. The varying sensitivity of the losses to the leakage fraction was linked to the effects of the upstream potential field of the blade on a vortical structure originating from the outer part of the seal. This vortical structure affected the interaction between the leakage and mainstream flows as it grew to become the hub passage vortex. Very limited cooling was provided by the leakage flows. The coolant was mainly concentrated close to the suction surface in the front part of the rotor platform and on the blade suction surface in the path of the passage vortex. However, the regions benefiting from cooling were also characterized by higher values of the heat transfer coefficient. As a consequence, the net heat flux reduction was small, and the leakage injection was thus deemed thermally neutral.

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Figures

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Fig. 1

Rim seal configuration and leakage injector

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Fig. 2

Overlapping seal geometry and location of control plane for calculating sealing effectiveness

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Fig. 3

Computational mesh

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Fig. 4

Loading distribution on T120 (low-speed)

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Fig. 5

Predicted iso-temperature surface at θ = (Tlocal - TL)/(T∞ - TL) = 0.99 (LF = 1.0% and VCAV,REL = 50%U)

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Fig. 6

Measured and predicted total pressure coefficient (CPO) line contours superimposed over flood contours of leakage concentration at LF = 1.0% and VCAV,REL = 50%U

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Fig. 7

Rim seal aerothermodynamics in terms of streamlines in meridional plane

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Fig. 8

Hub endwall static pressure coefficient and flow patterns at LF = 1.0% and VCAV,REL = 50%U

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Fig. 9

Effects of leakage fraction on adiabatic cooling effectiveness at a fixed relative cavity velocity of 50%U

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Fig. 10

Effects of relative cavity velocity on adiabatic cooling effectiveness at a leakage fraction of 1.0%

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Fig. 11

Predicted effects of leakage injection on heat transfer and cooling effectiveness in endwall region

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Fig. 12

Predicted net heat flux reduction parameter at VCAV,REL = 50%U

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Fig. 13

Overall seal performance in terms of aerodynamic losses and sealing effectiveness

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Fig. 14

Effects of relative cavity velocity on adiabatic cooling at higher leakage fraction (LF = 1.5%)

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Fig. 16

Radial velocity normalized by the blade speed at the seal exit plane and limiting streamlines on hub endwall at VCAV,REL = 50%U

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Fig. 15

Predicted overall performance in terms of losses and sealing effectiveness at VCAV,REL = 50%U

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