Research Papers

Effect of Nozzle Guide Vane Lean Under Influence of Inlet Temperature Traverse

[+] Author and Article Information
A. Rahim

e-mail: amir.rahim@eng.ox.ac.uk

L. He

Department of Engineering Science,
University of Oxford,
Oxford OX1 3PJ, UK

E. Romero

Turbine Systems,
Rolls-Royce PLC,
Moore Lane,
Derby DE24 8BJ, UK

Contributed by the International Gas Turbine Institute (IGTI) of ASME for publication in the JOURNAL OF TURBOMACHINERY. Manuscript received July 13, 2013; final manuscript received September 3, 2013; published online December 27, 2013. Editor: Ronald Bunker.

J. Turbomach 136(7), 071002 (Dec 27, 2013) (12 pages) Paper No: TURBO-13-1155; doi: 10.1115/1.4025947 History: Received July 13, 2013; Revised September 03, 2013

One of the most widely studied parameters in turbine blade shaping is blade lean, i.e., the tangential displacement of spanwise sections. However, there is a lack of published research that investigates the effect of blade lean under nonuniform temperature conditions (commonly referred to as a “hot-streak”) that are present at the combustor exit. Of particular interest is the impact of such an inflow temperature profile on heat transfer when the nozzle guide vane (NGV) blades are shaped. In the present work, a computational study has been carried out for a transonic turbine stage using an efficient unsteady Navier–Stokes solver (HYDRA). The configurations with a nominal vane and a compound leaned vane under uniform and hot-streak inlet conditions are analyzed. After confirming the typical NGV loading and aeroloss redistributions as seen in previous literature on blade lean, the focus has been directed to the rotor aerothermal behavior. While the overall stage efficiencies for the configurations are largely comparable, the results show strikingly different rotor heat transfer characteristics. For a uniform inlet, a leaned NGV has a detrimental effect on the rotor heat transfer. However, once the hot-streak is introduced, the trend is reversed; the leaned NGV leads to favorable heat transfer characteristics in general and for the rotor tip region in particular. The possible causal links for the observed aerothermal features are discussed. The present findings also highlight the significance of evaluating NGV shaping designs under properly conditioned inflow profiles, rather than extrapolating the wisdom derived from uniform inlet cases. The results also underline the importance of including rotor heat transfer and coolability during the NGV design process.

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Fig. 1

Three-passage HP turbine stage domain and surface mesh distribution for (a) nominal and (b) leaned vane arrangements

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Fig. 2

Inlet hot-streak profile

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Fig. 3

Radial variation of pitch-averaged temperature

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Fig. 4

Blade-to-blade static pressure distribution

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Fig. 5

NGV surface isentropic Mach numbers at 50% and 90% span sections for nominal and leaned cases

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Fig. 6

Vane suction surface streamline movement and corner vortex formation

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Fig. 7

Total pressure loss coefficient at NGV exit

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Fig. 8

Radial plot of absolute yaw angle at vane exit

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Fig. 9

Mass flux contours on NGV exit plane (dashed line indicates wake)

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Fig. 10

Streamline traces on mesh plane close to pressure surface and mass flux contours on the NGV exit plane

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Fig. 11

Radial plot of pitch-average mass flux at vane exit

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Fig. 12

Axial velocity contours at NGV exit (uniform inlet)

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Fig. 13

Axial velocity contours at NGV exit (hot-streak)

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Fig. 14

Radial plot of relative yaw angle at rotor inlet

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Fig. 15

Velocity diagrams at rotor inlet near to the tip (velocity triangles AB′C′ and ab′c′ indicate hot-streak cases)

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Fig. 16

Radial plot of relative total pressure at rotor inlet

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Fig. 17

Heat flux contours on rotor pressure surface

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Fig. 18

Heat fluxes and streamline patterns on rotor suction surface

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Fig. 19

Pressure differences on rotor pressure surface, normalized by the local relative dynamic head (Eq. (6)) (arrows indicate pressure gradient directions)

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Fig. 20

Heat flux on rotor tip (uniform inlet)

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Fig. 21

Heat flux on rotor tip (hot-streak inlet)

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Fig. 22

HTC and Taw (time-averaged) on rotor pressure surface

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Fig. 23

Radial variations of pitch-averaged relative total temperature at rotor inlet

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Fig. 24

Simplified single blade passage

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Fig. 25

Temperature profiles for uniform and hot-streak inlet




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