Research Papers

Impact of Nonuniform Leading Edge Coatings on the Aerodynamic Performance of Compressor Airfoils

[+] Author and Article Information
Michael E. Elmstrom

 Portsmouth Naval Shipyard, Portsmouth, NH 03904

Knox T. Millsaps

Mechanical and Astronautical Engineering, Naval Postgraduate School, Monterey, CA 93943millsaps@nps.edu

Garth V. Hobson

Mechanical and Astronautical Engineering, Naval Postgraduate School, Monterey, CA 93943

Jeffrey S. Patterson

Carderock Division, NSWC, Philadelphia, PA 19112

J. Turbomach 133(4), 041004 (Apr 19, 2011) (9 pages) doi:10.1115/1.3213550 History: Received September 01, 2008; Revised February 22, 2009; Published April 19, 2011; Online April 19, 2011

A computational fluid dynamic (CFD) investigation is presented that provides predictions of the aerodynamic impact of uniform and nonuniform coatings applied to the leading edge of a compressor airfoil in a cascade. Using a NACA 65(12)10 airfoil, coating profiles of varying leading edge nonuniformity were added. A nonuniform coating is obtained when a liquid coating is applied to a surface with high curvature, such as an airfoil leading edge. The CFD code used, RVCQ3D, is a Reynolds averaged Navier–Stokes solver, with a k-omega turbulence model. The code predicted that these changes in leading edge shape can lead to alternating pressure gradients in the first few percent of chord that create small separation bubbles and possibly early transition to turbulence. The change in total pressure loss and trailing edge deviation are presented as a function of a coating nonuniformity parameter. Results are presented over a range of negative and positive incidences and inlet Mach numbers from 0.6 to 0.8. A map is provided that shows the allowable degree of coating nonuniformity as a function of incidence and inlet Mach number.

Copyright © 2011 by American Society of Mechanical Engineers
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Figure 1

Schematic of a compressor airfoil leading edge for bare metal, uniform coating, and a typical, nonuniform coating

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Figure 2

Cartoon of the velocity distributions over the suction side of an airfoil: the normal distribution occurs with an uncoated blade at or near design incidence and the distribution with the spike occurs for poor leading edge geometry or with significant positive incidence

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Figure 3

Flow near the leading edge of a nonuniformly coated compressor airfoil where separation occurs with a turbulent reattachment

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Figure 4

Uncoated and coated leading edge geometries for various coating nonuniformities (k). The dimensions shown are in mils (thousands of an inch).

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Figure 5

Pressure coefficient downstream of the stagnation point, on the suction side, near the leading edge: these calculations are with i=0 and a Mach number of 0.70

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Figure 6

Total pressure loss coefficient and total cascade turning for an uncoated airfoil, a uniformly coated airfoil, and a series of nonuniformly coated airfoils: the inlet Mach number is 0.60 for all cases

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Figure 7

Effect of incident Mach number on the total pressure loss and cascade turning for 1 deg of positive incidence

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Figure 8

Velocity vectors near the location of a small-scale separation bubble that occurs just downstream of the coating nonuniformity

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Figure 9

Velocity vectors near the location of a large-scale separation bubble that occurs due to high coating nonuniformity and high positive incidence

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Figure 10

Map showing combinations of incidence and k, coating nonuniformity parameter that leads to no leading edge separation bubbles (in the left middle), and combinations that lead to separation bubbles on the suction and pressure sides



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