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TECHNICAL PAPERS

# Surface Roughness Effects on Turbine Blade Aerodynamics

[+] Author and Article Information
Frank Hummel, Michael Lötzerich

ALSTOM Power (Switzerland), Brown Boveri Strasse 7, CH-5401 Baden, Switzerland

Pasquale Cardamone

Institut für Strahlantriebe, Universität der Bundeswehr München, Werner-Heisenberg-Weg 39, D- 85577 Neubiberg, Germany

Leonhard Fottner1

Institut für Strahlantriebe, Universität der Bundeswehr München, Werner-Heisenberg-Weg 39, D- 85577 Neubiberg, Germany

1

Deceased.

J. Turbomach 127(3), 453-461 (Mar 01, 2004) (9 pages) doi:10.1115/1.1860377 History: Received October 01, 2003; Revised March 01, 2004

## Abstract

The aerodynamic performance of a turbine blade was evaluated via total pressure loss measurements on a linear cascade. The Reynolds number was varied from 600 000 to 1 200 000 to capture the operating regime for heavy-duty gas turbines. Four different types of surface roughness on the same profile were tested in the High Speed Cascade Wind Tunnel of the University of the German Armed Forces Munich and evaluated against a hydraulically smooth reference blade. The ratios of surface roughness to chord length for the test blade surfaces are in the range of $Ra∕c=7.6×10−06–7.9×10−05$. The total pressure losses were evaluated from wake traverse measurements. The loss increase due to surface roughness was found to increase with increasing Reynolds number. For the maximum tested Reynolds number of $Re=1200000$ the increase in total pressure loss for the highest analysed surface roughness value of $Ra=11.8μm$ was found to be 40% compared to a hydraulically smooth surface. The results of the measurements were compared to a correlation from literature as well as to well-documented measurements in literature. Good agreement was found for high Reynolds numbers between the correlation and the test results presented in this paper and the data available from literature.

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## Figures

Figure 1

The test facility (HGK) at UniBw Munich

Figure 2

Test blade geometry and design operating condition

Figure 13

Total pressure loss from wake traverse measurements of the double pitot probe for test blade 2, rough part compared to smooth part. Ma2,th=0.75, β1=133.3deg, Re2,th=600000.

Figure 14

Total pressure loss from wake traverse measurements of the double pitot probe for test blade 2, rough part compared to smooth part. Ma2,th=0.75, β1=133.3deg, Re2,th=900000.

Figure 15

Total pressure loss from wake traverse measurements of the double pitot probe for test blade 2, rough part compared to smooth part. Ma2,th=0.75, β1=133.3deg, Re2,th=1200000

Figure 16

Total pressure loss coefficient from wake traverse measurements of the double pitot probe for test blade 1, rough part compared to smooth part. Ma2,th=0.75 in comparison to 5-hole probe traverse results for the assumed hydraulically smooth test blade. FLS: 5-hole probe, DP: double pitot.

Figure 17

Total pressure loss coefficient from wake traverse measurements of the double pitot probe (DP) and five-hole probe (FLS) for test blade 2, rough part compared to smooth part. Ma2,th=0.75 and Ma2,th=0.85.

Figure 18

Row efficiency change due to surface roughness for loss model according to Eq. 1. Parameter Ra∕ks variation.

Figure 19

Row efficiency change due to surface roughness from loss model according to Eq. 1. Parameter ks∕Ra=5.2, comparison to experimental data.

Figure 3

Test blades with surface finish treatment

Figure 4

Position of double pitot probe behind test blade 1

Figure 5

Surface isentropic Mach number distribution for β1=133.3deg, Ma2,th=0.75 in dependence on Reynolds number

Figure 6

Surface isentropic Mach number distribution for β1=133.3deg, Ma2,th=0.85 in dependence on Reynolds number

Figure 7

Surface isentropic Mach number distribution for β1=143.3deg, Ma2,th=0.75 in dependence on Reynolds number

Figure 8

Surface isentropic Mach number distribution for β1=143.3deg, Ma2,th=0.85 in dependence on Reynolds number

Figure 9

Wake traverse measurements of total pressure for test blade 2, rough part under nominal boundary conditions. Comparison between five-hole probe (FLS) and double pitot (DP).

Figure 10

Total pressure loss from wake traverse measurements of the double pitot probe for test blade 1, rough part compared to smooth part. Ma2,th=0.75, β1=133.3deg, Re2,th=600000.

Figure 11

Total pressure loss from wake traverse measurements of the double pitot probe for test blade 1, rough part compared to smooth part. Ma2,th=0.75, β1=133.3deg, Re2,th=900000.

Figure 12

Total pressure loss from wake traverse measurements of the double pitot probe for test blade 1, rough part compared to smooth part. Ma2,th=0.75, β1=133.3deg, Re2,th=1200000.

## Errata

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