Research Papers: Gas Turbines: Industrial & Cogeneration

Numerical Investigation of Ash Deposition on Nozzle Guide Vane Endwalls

[+] Author and Article Information
Brian P. Casaday

e-mail: casaday.1@osu.edu

Ali A. Ameri

e-mail: ameri.1@osu.edu

Jeffrey P. Bons

e-mail: bons.2@osu.edu
Department of Mechanical
and Aerospace Engineering,
Ohio State University,
Columbus, OH 43235

Contributed by the International Gas Turbine Institute (IGTI) of ASME for publication in the Journal of Engineering for Gas Turbines and Power. Manuscript received July 17, 2012; final manuscript received July 26, 2012; published online February 11, 2013. Editor: Dilip R. Ballal.

J. Eng. Gas Turbines Power 135(3), 032001 (Feb 11, 2013) (9 pages) Paper No: GTP-12-1287; doi: 10.1115/1.4007736 History: Received July 17, 2012; Revised July 26, 2012

A computational study was performed to determine the factors that affect ash deposition rates on the endwalls in a nozzle guide vane passage. Deposition tests were simulated in flow around a flat plate with a cylindrical leading edge, as well as through a modern, high-performance turbine vane passage. The flow solution was first obtained independent of the presence of particulates, and individual ash particles were subsequently tracked using a Lagrangian tracking model. Two turbulence models were applied, and their differences were discussed. The critical viscosity model was used to determine particle deposition. Features that contribute to endwall deposition, such as secondary flows, turbulent dispersion, or ballistic trajectories, were discussed, and deposition was quantified. Particle sizes were varied to reflect Stokes numbers ranging from 0.01 to 1.0 to determine the effect on endwall deposition. Results showed that endwall deposition rates can be as high as deposition on the leading edge for particles with a Stokes number less than 0.1, but endwall deposition rates for a Stokes number of 1.0 were less than 25% of the deposition rates on the leading edge or pressure surface of the turbine vane. Deposition rates on endwalls were largest near the leading edge stagnation region on both the cylinder and vane geometries, with significant deposition rates downstream showing a strong correlation to the secondary flows.

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Fig. 1

Computational grids used in study. (a) Flat plate with cylindrical leading edge and flat endwalls. (b) Rolls Royce SSRevA turbine vane with flat endwalls.

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Fig. 2

Deposition on a serviced CFM56 turbine vane. (a) Digital image. (b) Red hue saturation image from Fig. 2(a).

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Fig. 3

JPBS ash deposition on a CFM56 vane from Webb et al. [18]

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Fig. 4

Velocity contours in z-direction at a distance of z/D = 0.1 from endwall. Negative values are velocities toward endwall; positive velocities are away from endwall.

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Fig. 5

Ash deposition rates on flat endwall of leading edge. Stk = 0.25.

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Fig. 6

Ash deposition rates on flat endwall of vane passage. Stk = 0.25.

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Fig. 7

Deposition rates at leading edge and upstream of leading edge. Horizontal trend = endwall deposition; vertical trend = leading edge deposition. Stk = 0.25.

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Fig. 8

Normalized static temperature through the vane passage at z/D = 0.1

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Fig. 9

Endwall deposition using k-ω model (a) without random walk correction and (b) with random walk correction. Stk = 0.25. (Compare with Fig. 5.)

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Fig. 10

Endwall ash deposition on flow around a cylinder with flat endwalls (a) 0.635 cm diameter and (b) 1.27 cm diameter

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Fig. 11

Endwall deposition upstream of leading edge (taken from Fig. 10)

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Fig. 12

Leading edge deposition. Stk = 0.25.

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Fig. 13

Deposition flux through stages around leading edge and 3D composite axial velocity contours. Stk = 0.25. (a) x/D = –0.5; (b) x/D = 0.5; (c) x/D = 1.5; (d) x/D = 2.5.

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Fig. 14

Deposition rates in stagnation region on leading edge and horseshoe vortex region on endwall




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