Research Papers

Large Eddy Simulations of Discrete Hole Film Cooling With Plenum Inflow Orientation Effects

[+] Author and Article Information
Sumanta Acharya

e-mail: acharya@tigers.LSU.edu

David Houston Leedom

Turbine Innovation and Energy Research (TIER) Center,
Department of Mechanical Engineering,
Louisiana State University,
Baton Rouge, LA 70803

1Corresponding author.

2Work done while the author was a graduate student.

Manuscript received March 26, 2012; final manuscript received September 14, 2012; published online December 6, 2012. Assoc. Editor: Akshai Runchal.

J. Heat Transfer 135(1), 011010 (Dec 06, 2012) (12 pages) Paper No: HT-12-1132; doi: 10.1115/1.4007667 History: Received March 26, 2012; Revised September 14, 2012

Large eddy simulations of film cooling from a discrete hole inclined 35 deg and fed by a plenum chamber are performed at a density ratio of 2 and blowing ratios from 0.5 to 2.0. Cylindrical holes at a length to diameter ratio of 1.75 and 3.5 are simulated issuing into a crossflow at a Reynolds number of approximately 16,000 based on freestream velocity and hole diameter. In addition to the baseline case of vertical inflow into the plenum, flow orientation into the plenum chamber parallel to and perpendicular to the mainstream flow are investigated. The predicted results are validated with reported measurements of the flow field and surface adiabatic effectiveness. Results show that the longer delivery tubes (L/D = 3.5) have higher cooling effectiveness except in the very near field of the coolant hole. The flow orientation in the plenum is demonstrated to have a significant effect on cooling effectiveness and on flow behavior in the delivery tube and downstream of the hole. The perpendicular plenum inflow exhibits the lowest cooling effectiveness, the lowest discharge coefficients, asymmetric jetting behavior, swirl, and a low-velocity core at the exit of the delivery tube. The parallel plenum flow orientation is shown to exhibit the highest cooling effectiveness and discharge coefficients.

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Fig. 1

Schematic of the computational domain and crossflow orientations. A is the baseline case, D and E are parallel (to the freestream) plenum inflow cases, and F and G are perpendicular (to the freestream) plenum inflow cases.

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Fig. 2

Grid independence study results for centerline adiabatic effectiveness (x/D = 0 is at the back edge of the hole exit)

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Fig. 3

Validation of first order statistics (mean centerline u and v velocities) and second-order statistics (centerline urms and vrms; x/D = 0 is the back edge of the hole exit)

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Fig. 4

Validation of first order statistics at the hole exit (y/ D = 0.05, x/D = 0.6; x/D = 0 is at the back edge of the hole exit)

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Fig. 5

Comparison of cooling effectiveness predictions, BR = 1, L/D = 1.75, case K-1-A (a) centerline effectiveness (x/ D = 0 is at the back edge of the hole exit) and (b) lateral effectiveness

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Fig. 6

Local surface adiabatic effectiveness for different BR and L/D values (x/D = 0 is at center of hole exit)

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Fig. 7

(a) Centerline surface adiabatic effectiveness and (b) laterally averaged surface adiabatic effectiveness (x/D = 0 is at the back edge of the hole exit)

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Fig. 8

Mean vertical velocity component at different y/D planes (y/D = 0 is the hole exit plane, freestream flow is from left to right)

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Fig. 9

Turbulent kinetic energy for blowing ratios of 0.5 (left) and 2 (right), and for L/D = 3.5 (top) and 1.75 (bottom). The second and fourth row show cross-planes at x/D = 3 and through the tube center. (x/D = 0 is at the center of the hole exit.)

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Fig. 10

Surface adiabatic effectiveness contours with superimposed streamlines at y/D = 0.01, L/D = 3.5, BR = 1—(top to bottom) upward plenum flow, parallel plenum inflow at up/uinf = 0.41, parallel plenum inflow at up/uinf = 1, perpendicular plenum inflow at up/uinf = 0.41, perpendicular plenum inflow at up/uinf = 1. (x/D = 0 is at center of hole exit.)

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Fig. 11

Laterally averaged adiabatic effectiveness for different plenum inflow cases (x/D = 0 is at center of hole exit)

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Fig. 12

Contours of vertical velocity magnitude at different in-tube cross-section planes for the different cases

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Fig. 13

Pathlines illustrating the origin of the center vortex for the perpendicular plenum inflow case; shading reflects temperature variations (for a qualitative perspective)

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Fig. 14

Jet shape with velocity vectors and temperatures at three hole diameters downstream of the hole exit (x/D = 3) for vertical plenum inflow (H-1-A), parallel plenum inflow (H-1-D and H-1-E) and perpendicular plenum inflow (H-1-F and H-1-G) cases




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