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Research Papers

Numerical Investigation of the Influence of Real World Blade Profile Variations on the Aerodynamic Performance of Transonic Nozzle Guide Vanes

[+] Author and Article Information
R. Edwards, A. Asghar, R. Woodason, M. LaViolette, K. Goni Boulama, W. D. E. Allan

 Royal Military College of Canada, Kingston, ON, K7K 7B4, Canada

J. Turbomach 134(2), 021014 (Jun 28, 2011) (8 pages) doi:10.1115/1.4003050 History: Received June 04, 2010; Revised July 22, 2010; Published June 28, 2011; Online June 28, 2011

This paper addresses the issue of aerodynamic consequences of small variations in airfoil profile. A numerical comparison of flow field and cascade pressure losses for two representative repaired profiles and a reference new vane were made. Coordinates for the three airfoil profiles were obtained from the nozzle guide vanes of refurbished turboshaft engines using 3D optical scanning and digital modeling. The repaired profiles showed differences in geometry in comparison with the new vane, particularly near the leading and trailing edges. A numerical simulation was conducted using a commercial CFD code, which uses the finite volume approach for solving the governing equations. The computational predictions of the aerodynamic performance were compared with experimental results obtained from a cascade consisting of blades with the same airfoil profiles. The CFD analysis was performed for the cascade at subsonic inlet and transonic exit conditions. Boundary layer growth, wake formation, and shock boundary layer interactions were observed in the two-dimensional computations. The flow field showed the presence of shock waves downstream of the passage throat and near the trailing edges of the blades. A conspicuous change in flow pattern due to subtle variation in airfoil profile was observed. The calculated flow field was compared with the flow pattern visualized in the experimental test rig using the schlieren method. The total pressure calculation for the cascade exit showed an increase in pressure loss for one of the off-design profiles. The pressure loss calculations were also compared with the multihole total pressure probe measurement in the transonic cascade rig.

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Copyright © 2012 by American Society of Mechanical Engineers
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Figures

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Figure 1

Three profiles of a cascade blade: (a) overall detail, (b) differences at the leading edge, and (c) differences near trailing edge

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Figure 2

Cascade parameters and pressure measurement locations

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Figure 3

Computational domain

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Figure 4

Changes in mass flow with backpressure for the RV1 airfoil

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Figure 5

Mesh refinement: (a) around the airfoil and (b) close to the surface near the trailing edge

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Figure 6

Schlieren images and computed axial density gradient of the shock flow pattern for each profile

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Figure 7

Computed surface Mach number of the RV1 airfoil

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Figure 8

Computed Mach number in the cascade

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Figure 9

Total pressure distribution for three profiles

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Figure 10

Cascade exit Mach number for three profiles

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Figure 11

Outlet angle for three profiles

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Figure 12

Choked flow condition for RV1 airfoil: (a) computed axial density gradient and (b) Mach number

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