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Research Papers: Gas Turbines: Turbomachinery

Prediction of Sand Transport and Deposition in a Two-Pass Internal Cooling Duct

[+] Author and Article Information
Sukhjinder Singh

Mem. ASME
Department of Mechanical Engineering,
Virginia Tech,
Blacksburg, VA 24061
e-mail: singh@vt.edu

Danesh K. Tafti

Fellow ASME
Department of Mechanical Engineering,
Virginia Tech,
213E Goodwin Hall,
Blacksburg, VA 24061
e-mail: dtafti@exchange.vt.edu

1Corresponding author.

Contributed by the Turbomachinery Committee of ASME for publication in the JOURNAL OF ENGINEERING FOR GAS TURBINES AND POWER. Manuscript received October 22, 2015; final manuscript received November 29, 2015; published online February 17, 2016. Editor: David Wisler.

J. Eng. Gas Turbines Power 138(7), 072606 (Feb 17, 2016) (12 pages) Paper No: GTP-15-1500; doi: 10.1115/1.4032340 History: Received October 22, 2015; Revised November 29, 2015

Sand transport and deposition is investigated in a two-pass internal cooling ribbed geometry at near engine conditions. Large-eddy simulation (LES) calculations are performed for bulk Reynolds number of 25,000 to calculate flow field and heat transfer. Constant wall temperature boundary condition is used to investigate the effect of temperature on particle deposition. Three different wall temperatures of 950 °C, 1000 °C, and 1050 °C are considered. Particle sizes in range 5–25 μm are considered. A new deposition model which accounts for particle composition, temperature, impact velocity and angle and material properties of particle and surface is developed and applied. Calculated impingement and deposition patterns are discussed for different exposed surfaces in the two pass geometry. Other than the leading rib faces, the highest particle impingement and deposition is observed in the bend region and first quarter of the second pass. Significant deposition is observed in the two pass geometry for all three wall temperatures considered. Particle impingement and hence deposition is dominated by larger particles except in the downstream half of the bend region. In total, approximately 38%, 59%, and 67% of the injected particles deposit in the two passes, for the three wall temperatures of 950 °C, 1000 °C, and 1050 °C, respectively. While particle impingement is highest for wall temperature of 950 °C, higher deposition is observed for 1000 °C and 1050 °C cases. Deposition increases significantly with wall temperature. For 1000 °C, roughly 12% of the impacting particles deposit. For 1050 °C, approximately 23% of the particles deposit on impact. For all the three cases, the second pass experiences higher deposition compared to the first pass due to higher turbulence and direct impingement.

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References

Figures

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Fig. 2

Normal COR for different particle sizes versus normal impact velocity

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Fig. 3

Probability of sticking as a function of COR

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Fig. 4

Probability of sticking based on viscosity (Pvisc) with temperature

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Fig. 1

Computational domain showing view of two passes with pitch numbering

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Fig. 5

Sticking probability contours (a) 5 μm and (b) 25 μm for normal collisions

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Fig. 6

Mean streamline distribution in a pitch length at the z symmetry plane

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Fig. 7

Mean streamline distribution at a plane parallel to ribbed wall, 0.5Dh away (pitch # 11-23)

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Fig. 8

Instantaneous turbulent eddies in the computational domain

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Fig. 9

Contours of (a) particle impingement and (b) particle deposition on the ribbed surface for wall temperature of 950 °C

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Fig. 10

Contours of (a) particle impingement and (b) particle deposition on the ribbed surface for wall temperature of 1000 °C

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Fig. 11

Contours of (a) particle impingement and (b) particle deposition on the ribbed surface for wall temperature of 1050 °C

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Fig. 12

Scatter plot of impacting particle diameters on (going clockwise) ribbed surface, end wall, and outer sidewall of second pass for pitch #13-21. (Tw = 950 °C).

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Fig. 13

Contour plots of (a) average impact velocity and (b) average impact angle on the (going clockwise) ribbed surface, end wall and outer sidewall of second pass for pitch #13-21 (Tw = 950 °C)

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Fig. 14

Contours of particle impingement and deposition on the outer sidewall of the second pass (pitch # 18-23) for the wall temperature of (a) 950 °C, (b) 1000 °C, and (c) 1050 °C

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Fig. 15

Particle impingement on rib surface facing flow (a) and deposition (b) on rib faces in six ribs upstream and downstream of the bend (pitch# shown) (Tw = 1000 °C)

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Fig. 16

Particle impingement and deposition at the end wall surface (Tw = 1000 °C)

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Fig. 17

Number of particles entering each pitch

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Fig. 18

Total number of particle impacts per pitch normalized by the pitch area and the number of particles injected

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Fig. 19

Number of particles deposited, ndep, normalized by the number of particles entering the pitch (npitch)

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