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Research Papers: Gas Turbines: Oil and Gas Applications

Numerical Analysis of the Effects of Nonuniform Surface Roughness on Compressor Stage Performance

[+] Author and Article Information
Mirko Morini, Michele Pinelli, Pier Ruggero Spina

Dipartimento di Ingegneria, Università degli Studi di Ferrara, Via Saragat, 1-44122 Ferrara, Italy

Mauro Venturini1

Dipartimento di Ingegneria, Università degli Studi di Ferrara, Via Saragat, 1-44122 Ferrara, Italymventurini@ing.unife.it

1

Corresponding author.

J. Eng. Gas Turbines Power 133(7), 072402 (Mar 24, 2011) (8 pages) doi:10.1115/1.4002350 History: Received May 31, 2010; Revised July 29, 2010; Published March 24, 2011; Online March 24, 2011

Gas turbine performance degradation over time is mainly due to the deterioration of compressor and turbine blades, which, in turn, causes a modification of the compressor and turbine performance maps. Since the detailed information about the actual modification of the compressor and turbine performance maps is usually unavailable, the component performance can be modeled and investigated by the following: scaling the overall performance map, using stage-by-stage models of the compressor and turbine, and scaling each single stage performance map to account for each stage deterioration, or performing 3D numerical simulations, which allow to both highlight the fluid-dynamic phenomena occurring in the faulty component and grasp the effect on the overall performance of each affected component. In this paper, the authors address the most common and experienced source of loss for a gas turbine, i.e., compressor fouling. With respect to the traditional approach, which mainly aims at the identification of the overall effects of fouling, authors investigate a microscale representation of compressor fouling (i.e., blade surface deterioration and flow deviation). This allows (i) a more detailed investigation of the fouling effects (e.g., mechanism, location along blade height, etc.), (ii) a more extensive analysis of the causes of performance deterioration, and (iii) the assessment of the effect of fouling on stage performance coefficients and on stage performance maps. In this paper, the effect of nonuniform surface roughness on both rotor and stator blades of an axial compressor stage is investigated by using a commercial CFD code. The NASA Stage 37 test case is considered as the baseline geometry and a numerical model already validated against experimental data available in literature is used for the simulations. Different nonuniform combinations of surface roughness levels are imposed on rotor and stator blades. This makes it possible to highlight how the localization of fouling on compressor blades affects compressor performance both at an overall and at a fluid-dynamic level.

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Copyright © 2011 by American Society of Mechanical Engineers
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Figures

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Figure 1

Modeled geometry (a) and numerical grid (b)

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Figure 2

Compressor stage performance maps

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Figure 3

Relative velocity downstream rotor

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Figure 4

Roughened rotor and stator: radial profiles of pitchwise mass-averaged stage total pressure ratio

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Figure 5

Roughened rotor and stator: surface static pressure distributions at 50% span

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Figure 6

Roughened rotor and stator: compressor stage performance map

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Figure 7

Roughened rotor and stator: total pressure profile along streamwise direction

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Figure 8

Roughened rotor blade surfaces: compressor stage performance map

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Figure 9

Roughened rotor blade surfaces: surface static pressure distributions at 50% span

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Figure 10

Roughened rotor blade surfaces: relative Mach number profile

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Figure 11

Numerical streamline on rotor suction surface for different roughness combinations

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Figure 12

Relative Mach number profiles and suction surface streamline at different span positions: RouRot-Ss (top) and SmRot-SmStat (bottom)

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