The overall efficiency and operational behavior of aircraft engines are influenced by the surface finish of the airfoils. During operation, the surface roughness significantly increases due to erosion and deposition processes. The aim of this study is to analyze the influence of roughness on the aerodynamics of the low-pressure turbine (LPT) of a midsized high bypass turbofan. In order to gain a better insight into the operational roughness structures, a sample of new, used, cleaned, and reworked turbine blades and vanes are measured using the confocal laser scanning microscopy technique. The measurement results show local inhomogeneities. The roughness distributions measured are then converted into their equivalent sand grain roughness ks,eq to permit an evaluation of the impact on aerodynamic losses. The numerical study is performed using the computational fluid dynamics (CFD)-solver turbomachinery research aerodynamics computational environment (TRACE) which was validated before with the existing data from rig experiments. It is observed that the influence of the surface roughness on the turbine efficiency is significant at take-off but negligible at cruise. A detailed analysis on the aerodynamics at take-off shows that very rough airfoils lead to higher profile and secondary loss. Due to the higher disturbances present in flows circulating over rough walls, the transition occurs earlier, and the momentum thickness increases in the turbulent boundary layer. The service-induced roughness structures cause an efficiency drop in the LPT of ηT=0.16% compared to new parts. A gas path analysis showed that this results in an increased fuel flow of Δm˙f=+0.06% and an exhaust gas temperature (EGT) rise of ΔEGT=+1.2K for fixed engine pressure ratio which is equivalent to roughly 4% of the typical EGT margin of a fully refurbished engine. This result stresses the importance of roughness-induced loss in LPTs.

References

References
1.
Wisler
,
D. C.
,
1998
, “
The Technical and Economic Relevance of Understanding Blade Row Interaction Effects in Turbomachinery
,” (Lecture Series, Vol. 2), von Karman Institute of Fluid Dynamics, Sint-Genesius-Rode, Belgium, pp. H1–H17.
2.
Vázquez
,
R.
,
Torre
,
D.
,
Partida
,
F.
,
Armañanzas
,
L.
, and
Antoranz
,
A.
,
2011
, “Influence of Surface Roughness in the Profile and End-Wall Losses in Low Pressure Turbines,”
ASME
Paper No. GT2011-46371.
3.
Vázquez
,
R.
, and
Torre
,
D.
,
2014
, “
The Effect of Surface Roughness on Efficiency of Low Pressure Turbines
,”
ASME J. Turbomach.
,
136
(
6
), p.
061008
.
4.
Hourmouziadis
,
J.
,
1989
, “
Aerodynamic Design of Low Pressure Turbines
,”
Blading Design for Axial Turbomachines
(AGARD Lecture Series), von Karman Institute for Fluid Dynamics, Sint-Genesius-Rode, Belgium.
5.
Schlichting
,
H.
, and
Gersten
,
K.
,
2017
,
Boundary-Layer Theory
,
9th ed
,
Springer-Verlag, Berlin
.
6.
Bons
,
J. P.
, and
Christensen
,
K. T.
,
2007
, “A Comparison of Real and Simulated Surface Roughness Characterizations,”
AIAA
Paper No. 2007-3997.
7.
Fiala
,
A.
, and
Kügeler
,
E.
,
2011
, “
Roughness Modeling for Turbomachinery
,”
ASME
Paper No. GT2011-45424.
8.
Feindt
,
E.
,
1956
, “
Untersuchungen über die Abhängigkeit des Umschlages laminarturbulent von der Oberflächenrauhigkeit und der Druckverteilung
,” Ph.D. dissertation, Technischen Universität Braunschweig, Braunschweig, Germany.
9.
Pinson
,
M. W.
, and
Wang
,
T.
,
2000
, “
Effect of Two-Scale Roughness on Boundary Layer Transition Over a Heated Flat Plate—Part 1: Surface Heat Transfer
,”
ASME J. Turbomach.
,
122
(
2
), pp.
301
307
.
10.
Roberts
,
S. K.
, and
Yaras
,
M. I.
,
2005
, “
Boundary-Layer Transition Affected by Surface Roughness and Free-Stream Turbulence
,”
ASME J. Fluids Eng.
,
127
(
3
), pp.
449
457
.
11.
Roberts
,
S. K.
, and
Yaras
,
M. I.
,
2006
, “
Effects of Surface-Roughness Geometry on Separation-Bubble Transition
,”
ASME J. Turbomach.
,
128
(
2
), pp.
349
356
.
12.
Bammert
,
K.
, and
Fiedler
,
K.
,
1966
, “
Hinterkanten- und Reibungsverlust in Turbinenschaufelgittern
,”
Forsch. Ing.
,
32
(
5
), pp.
133
141
.
13.
Bammert
,
K.
, and
Sandstede
,
H.
,
1973
, “
Strömungsverluste Durch Oberflächenrauheiten Der Schaufeln in Einer Turbine
,”
VDI-Ber.
,
193
, pp.
225
232
.
14.
Bammert
,
K.
, and
Sandstede
,
H.
,
1980
, “
Measurements of the Boundary Layer Development Along a Turbine Blade With Rough Surfaces
,”
ASME J. Eng. Power
,
102
(
4
), pp.
978
983
.
15.
Kind
,
R.
,
Serjak
,
P.
, and
Abbott
,
M.
,
1998
, “
Measurements and Prediction of the Effects of Surface Roughness on Profile Losses and Deviation in a Turbine Cascade
,”
ASME J. Turbomach.
,
120
(
1
), pp.
20
27
.
16.
Yun
,
Y. I.
,
Park
,
I. Y.
, and
Song
,
S. J.
,
2005
, “
Performance Degradation Due to Blade Surface Roughness in a Single-Stage Axial Turbine
,”
ASME J. Turbomach.
,
127
(
1
), pp.
137
143
.
17.
Taylor
,
R. T.
,
1990
, “
Surface Roughness Measurements on Gas Turbine Blades
,”
ASME J. Turbomach.
,
112
(
2
), pp.
175
180
.
18.
Bons
,
J. P.
,
Taylor
,
R. T.
,
McClain
,
S. T.
, and
Rivir
,
R. B.
,
2001
, “
The Many Faces of Turbine Surface Roughness
,”
ASME J. Turbomach.
,
123
(
4
), pp.
739
748
.
19.
Hohenstein
,
S.
,
Aschenbruck
,
J.
, and
Seume
,
J.
,
2013
, “Aerodynamic Effects of Non-Uniform Surface Roughness on a Turbine Blade,”
ASME
Paper No. GT2013-95433.
20.
DIN
,
1982
, “Form Deviations; Concepts; Classification System,” Normenausschus Technische Grundlagen, Berlin, Germany, Standard No.
DIN 4760
.http://standards.globalspec.com/std/456407/din-4760
21.
ISO
,
2013
, “Geometrical Product Specifications-Filtration—Part 21: Linear Profile Filters: Gaussian Filters,” International Organization for Standardization, Geneva, Switzerland, Standard No. 16610-21.
22.
ISO,
1998
, “Geometrical Product Specifications (GPS)-Surface Texture: Profile Method-Rules and Procedures for the Assessment of Surface Texture,” International Organization for Standardization, Geneva, Switzerland, Standard No.
BS EN ISO 4288:1998
.https://www.iso.org/standard/2096.html
23.
ISO,
2010
, “Geometrical Product Specifications-Surface Texture: Profile Method-Terms, Definitions and Surface Texture Parameters,” International Organization for Standardization, Geneva, Switzerland, Standard No. DIN EN ISO 4287.
24.
Hamed
,
A.
,
Tabakoff
,
W.
,
Rivir
,
R. B.
,
Das
,
K.
, and
Arora
,
P.
,
2005
, “
Turbine Blade Surface Deterioration by Erosion
,”
ASME J. Turbomach.
,
127
(
3
), pp.
445
452
.
25.
Tabakoff
,
W.
, and
Hamed
,
A.
,
1986
, “
The Dynamics of Suspended Solid Particles in a Two-Stage Gas Turbine
,”
ASME Turbomach.
,
108
(
2
), pp.
298
302
.
26.
Marciniak
,
V.
,
Kügeler
,
E.
, and
Franke
,
M.
,
2010
, “
Predicting Transition on Low-Pressure Turbine Profiles
,”
Fifth European Conference on Computational Fluid Dynamics
, Lisbon, Portugal, June 14–17, Paper No. 01622.
27.
Becker
,
K.
,
Heitkamp
,
K.
, and
Kügeler
,
2010
, “
Recent Progress in a Hybrid-Grid CFD Solver for Turbomachinery Flows
,”
Fifth European Conference on Computational Fluid Dynamics
(
ECCOMAS CFD
), Lisbon, Portugal, June 14–17, Paper No. 01609.https://www.researchgate.net/publication/225006412_Recent_Progress_In_A_Hybrid-Grid_CFD_Solver_For_Turbomachinery_Flows
28.
Roe
,
P.
,
1981
, “
Approximate Riemann Solvers, Parameter Vectors and Difference Schemes
,”
J. Comput. Phys.
,
43
(
2
), pp.
357
372
.
29.
Saxer
,
A. P.
, and
Giles
,
M. B.
,
1993
, “
Quasi-Three-Dimensional Nonreflecting Boundary Conditions for Euler Equation Calculation
,”
AIAA J. Propul. Power
,
9
(
2
), pp.
263
271
.
30.
Wilcox
,
D. C.
,
2006
,
Turbulence Modeling for CFD
,
3rd ed.
,
DCW Industries, Inc
, La Canada, CA.
31.
Kato
,
M.
, and
Launder
,
B. E.
,
1993
, “
The Modeling of Turbulent Flow Around Stationary and Vibrating Square Cylinders
,”
Nineth Symposium on Turbulent Shear Flows
, Kyoto, Japan, Aug. 16–18, Paper No.
10-4
.https://www.researchgate.net/publication/247931894_The_Modelling_of_Turbulent_Flow_Around_Stationary_and_Vibrating_Square_Cylinders
32.
Langtry
,
R. B.
, and
Menter
,
F. R.
,
2009
, “
Correlation-Based Transition Modeling for Unstructured Parallelized Computational Fluid Dynamics Codes
,”
AIAA J.
,
47
(
12
), pp.
2894
2906
.
33.
Dassler
,
P.
,
Kozulovic
,
D.
, and
Fiala
,
A.
,
2012
, “
An Approach for Modelling the Roughness-Induced Boundary Layer Transition Using the Transport Equations
,”
European Congress on Computational Methods in Applied Sciences and Engineering (ECCOMAS)
, Vienna, Austria, Sept. 10–14, Paper No. 1821.
34.
Vázquez
,
R.
,
Cadrecha
,
D.
, and
Torre
,
D.
,
2003
, “High Stage Loading Low Pressure Turbine: A New Proposal for an Efficient Chart,”
ASME
Paper No. GT2003-38374.
35.
Kurzke
,
J.
,
2005
, “How to Create a Performance Model of a Gas Turbine From a Limited Amount of Information,”
ASME
Paper No. GT2005-68536.
You do not currently have access to this content.