Abstract

Due to imperfection in the manufacturing process and in-service wear, fan blades in a turbofan engine do not have the same geometry. This lack of symmetry inevitably leads to difficulties in predicting the fan blades' running geometry in an assembly as blade variability is amplified by the aerodynamic and centrifugal loading. This variability can lead to an aeromechanical phenomenon termed “alternate passage divergence” (APD). As the name suggests, it manifests itself as alternating geometric and aerodynamic patterns in a fan assembly during operation. APD can potentially influence the fan performance, the stability, and the multiple pure tone (MPT)/“Buzz-Saw” noise and is therefore an important area of research. For this study, the APD phenomenon is purposely triggered on a transonic fan blade. A full-assembly computational domain with one mis-staggered blade is used to examine the whole assembly performance and the untwist behavior with APD. In particular, the influence of fan blade stiffness on the APD behavior is examined. The behavior of the current blade is compared with that of a blade used in a precursor study, and it is found that, under certain conditions, the blades show similar behavior even though they have distinctly different geometry features. This illustrates that it is important to understand the phenomenon as the accurate prediction of running geometry is vital at early design stage.

References

References
1.
Rugg
,
D.
,
2010
, “
Trends and Issues—Titanium Alloy Use in Gas Turbines
,” https://goo.gl/Hxzj6j, Accessed July 2, 2018.
2.
Wilson
,
M. J.
,
Imregun
,
M.
, and
Sayma
,
A. I.
,
2006
, “
The Effect of Stagger Variability in Gas Turbine Fan Assemblies
,”
ASME J. Turbomach.
,
129
(
2
), pp.
404
411
. 10.1115/1.2437776
3.
Stratford
,
B.
, and
Newby
,
D.
,
1977
, “
A New Look at the Generation of Buzz-Saw Noise
,”
4th AIAA Aeroacoustics Conference
,
Atlanta, GA
,
Oct. 3–5
, p.
1343
.
4.
Han
,
F.
,
Sharma
,
A.
,
Paliath
,
U.
, and
Shieh
,
C.
,
2014
, “
Multiple Pure Tone Noise Prediction
,”
J. Sound Vib.
,
333
(
25
), pp.
6942
6959
. 10.1016/j.jsv.2014.08.006
5.
McAlpine
,
A.
,
Fisher
,
M. J.
, and
Tester
,
B. J.
,
2006
, “
Buzz-Saw” Noise: A Comparison of Measurement With Prediction
,”
J. Sound Vib.
,
290
(
3–5
), pp.
1202
1233
. 10.1016/j.jsv.2005.05.028
6.
Stapelfeldt
,
S. C.
, and
Vahdati
,
M.
,
2018
, “
On the Importance of Engine-Representative Models for Fan Flutter Predictions
,”
ASME J. Turbomach.
,
140
(
8
), p.
081005
. 10.1115/1.4040110
7.
Sayma
,
A. I.
,
Vahdati
,
M.
,
Sbardella
,
L.
, and
Imregun
,
M.
,
2000
, “
Modeling of Three-Dimensional Viscous Compressible Turbomachinery Flows Using Unstructured Hybrid Grids
,”
AIAA J.
,
38
(
6
), pp.
945
954
. 10.2514/2.1062
8.
Spalart
,
P.
, and
Allmaras
,
S.
,
1992
, “
A One-Equation Turbulence Model for Aerodynamic Flows
,”
30th Aerospace Sciences Meeting and Exhibit, Aerospace Sciences Meetings
,
Reno, NV
,
Jan. 6–9
, p.
439
.
9.
Sayma
,
A. I.
,
Vahdati
,
M.
, and
Imregun
,
M.
,
2000
, “
An Integrated Nonlinear Approach for Turbomachinery Forced Response Prediction
,”
J. Fluids Struct.
,
14
(
1
), pp.
87
101
. 10.1006/jfls.1999.0253
10.
Marshall
,
J. G.
, and
Imregun
,
M.
,
1996
, “
An Analysis of the Aeroelastic Behaviour of a Typical Fan-Blade With Emphasis on the Flutter Mechanism
,”
ASME 1996 International Gas Turbine and Aeroengine Congress and Exhibition
, p.
V005T14A009
.
11.
Mayorca
,
M. A.
,
2011
, “
Numerical Methods for Turbomachinery Aeromechanical Predictions
,” Doctoral dissertation,
Royal Institute of Technology
,
Stockhom, Sweden
.
12.
Vahdati
,
M.
,
Simpson
,
G.
, and
Imregun
,
M.
,
2011
, “
Mechanisms for Wide-Chord Fan Blade Flutter
,”
ASME J. Turbomach.
,
133
(
6
), p.
041029
. 10.1115/1.4001233
13.
Choi
,
M.
,
Smith
,
N. S.
, and
Vahdati
,
M.
,
2012
, “
Validation of Numerical Simulation for Rotating Stall in a Transonic Fan
,”
ASME J. Turbomach.
,
135
(
2
), p.
021004
. 10.1115/1.4006641
14.
Stapelfeldt
,
S. C.
,
Parry
,
A. B.
, and
Vahdati
,
M.
,
2016
, “
Investigation of Flutter Mechanisms of a Contra-Rotating Open Rotor
,”
ASME J. Turbomach.
,
138
(
5
), p.
051009
. 10.1115/1.4032186
15.
Lee
,
K.
,
Wilson
,
M.
, and
Vahdati
,
M.
,
2017
, “
Numerical Study on Aeroelastic Instability for a Low-Speed Fan
,”
ASME J. Turbomach.
,
139
(
7
), p.
071004
. 10.1115/1.4035569
16.
Wilson
,
M. J.
,
2007
, “
The Effects of Blade Variability in Gas Turbine Fan Assemblies
,” Doctoral dissertation,
Imperial College London
,
London
.
17.
Denton
,
J. D.
, and
Xu
,
L.
,
2002
, “
The Effects of Lean and Sweep on Transonic Fan Performance
,”
ASME Turbo Expo: Power for Land, Sea, and Air, Volume 5: Turbo Expo
,
Amsterdam, Netherlands
,
June 3–6
, pp.
23
32
.
18.
Calvert
,
W. J.
, and
Ginder
,
R. B.
,
1999
, “
Transonic Fan and Compressor Design
,”
Proc. Inst. Mech. Eng., Part C
,
213
(
5
), pp.
419
436
. 10.1243/0954406991522671
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