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Research Papers

Large Eddy Simulations of Film-Cooling Flows With a Micro-Ramp Vortex Generator

[+] Author and Article Information
S. Pratap Vanka

Department of Mechanical Science and Engineering,
University of Illinois at Urbana-Champaign,
Urbana, Illinois, 61801
e-mail: spvanka@illinois.edu

1Corresponding author.

Contributed by International Gas Turbine Institute (IGTI) for the JOURNAL OF TURBOMACHINERY. Manuscript received May 28, 2011; final manuscript received August 18, 2011; published online October 18, 2012. Editor: David Wisler.

J. Turbomach 135(1), 011004 (Oct 18, 2012) (13 pages) Paper No: TURBO-11-1079; doi: 10.1115/1.4006329 History: Received May 28, 2011; Revised August 18, 2011

Large eddy simulations were performed to study the effect of a micro-ramp on an inclined turbulent jet interacting with a cross-flow in a film-cooling configuration. The micro-ramp vortex generator is placed downstream of the film-cooling jet. Changes in vortex structure and film-cooling effectiveness are evaluated. Coherent turbulent structures characteristic of a jet in a cross-flow are analyzed and the genesis of the counter-rotating vortex pair in the jet is discussed. Results are reported for two film-cooling configurations, where the primary difference is the way the jet inflow boundary conditions are prescribed. In the first configuration, the jet conditions are prescribed using a precursor simulation and in the second the jet is modeled using a plenum/pipe configuration. The latter configuration was designed based on previous wind tunnel experiments at NASA Glenn Research Center, and the present results are meant to supplement those experiments. It is found that the micro-ramp improves film-cooling effectiveness by generating near-wall counter-rotating vortices which help entrain coolant from the jet and transport it to the surface. The pair of vortices generated by the micro-ramp are of opposite sense to the vortex pair embedded in the jet.

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Figures

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Fig. 1

Computational domains for film-cooling configurations

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Fig. 6

Contours of mean streamwise vorticity overlaid with streamlines at x/d = 3.7 for case 1

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Fig. 5

Mean temperature at midspan (y/d = 0) for case 1

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Fig. 4

Instantaneous temperature at midspan (y/d = 0) for case 1

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Fig. 3

Instantaneous velocity magnitude at jet inflow (z/d=0) for case 1

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Fig. 2

Visualization of jet flow with no micro-ramp for case 1 using isosurface of instantaneous temperature at T* = 0.5

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Fig. 7

Contours of mean temperature at x/d = 3.7 for case 1

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Fig. 8

Mean temperature along wall of domain (z/d = 0) for case 1

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Fig. 10

Centerline and span-averaged film-cooling effectiveness for case 1

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Fig. 9

Vortex cores extracted from mean flow field for flow with no micro-ramp for case 1. Jet inflow perimeter is highlighted in red.

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Fig. 11

Predicted centerline film-cooling effectiveness for case 1 compared with DNS data from Muldoon and Acharya [10]

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Fig. 12

Comparison of instantaneous velocity magnitude at midspan (y/d = 0) for case 2

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Fig. 18

Contours of mean streamwise vorticity overlaid with streamlines at x/d = 4 for case 2

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Fig. 19

Contours of mean temperature at x/d = 4 for case 2

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Fig. 20

Mean temperature along wall of domain (z/d = 0) for case 2

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Fig. 16

Location of survey planes in near-field of jet for case 2

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Fig. 17

Streamwise evolution of the jet CRVP for case 2. Mean streamwise vorticity and mean velocity vectors are shown at streamwise planes in the jet near-field.

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Fig. 21

Centerline and span-averaged film-cooling effectiveness for case 2

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Fig. 23

Comparison of vortex core trajectories between the LES of case 2 and experiment

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Fig. 13

Mean velocity magnitude (a) and mean streamwise vorticity (b) at jet inflow (z/d = 0) for flow with no micro-ramp for case 2

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Fig. 14

Instantaneous temperature at midspan (y/d = 0) for case 2

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Fig. 15

Mean temperature at midspan (y/d = 0) for case 2

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Fig. 22

Comparison of predicted mean boundary-layer profile for case 2 versus experiment at centerline of domain (y/d = 0)

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