The aim of this paper is to introduce design modifications that can be made to improve the flutter stability of a fan blade. A rig fan blade, which suffered flutter in the part-speed range and for which good quality measured data in terms of steady flow and flutter boundary is available, is used for this purpose. The work is carried out numerically using the aeroelasticity code AU3D. Two different approaches are explored: aerodynamic modifications and aero-acoustic modifications. In the first approach, the blade is stabilized by altering the radial distribution of the stagger angle based on the steady flow on the blade. The re-staggering patterns used in this work are therefore particular to the fan blade under investigation. Moreover, the modifications made to the blade are very simple and crude, and more sophisticated methods and/or an optimization approach could be used to achieve the above objectives with a more viable final design. This paper, however, clearly demonstrates how modifying the steady blade aerodynamics can prevent flutter. In the second approach, flutter is removed by drawing bleed air from the casing above the tip of the blade. Only a small amount of bleed (0.2% of the total inlet flow) is extracted such that the effect on the operating point of the fan is small. The purpose of the bleed is merely to attenuate the pressure wave that propagates from the trailing edge to the leading edge of the blade. The results show that extracting bleed over the tip of the fan blade can improve the flutter margin of the fan significantly.

References

References
1.
Vahdati
,
M.
,
Sayma
,
A.
,
Marshall
,
J.
, and
Imregun
,
M.
,
2001
, “
Mechanisms and Prediction Methods for Fan Blade Stall Flutter
,”
J. Propulsion Power
,
17
(
5
), pp.
1100
1108
.
2.
Vahdati
,
M.
,
Simpson
,
G.
, and
Imregun
,
M.
,
2011
, “
Mechanisms for Wide-Chord Fan Blade Flutter
,”
J. Turbomach.
,
133
(
4
),
041029
.
3.
Vahdati
,
M.
,
Smith
,
N.
, and
Zhao
,
F.
,
2015
, “
Influence of Intake on Fan Blade Flutter
,”
J. Turbomach.
,
137
(
8
), pp.
081002
.
4.
Vahdati
,
M.
, and
Cumpsty
,
N.
,
2015
, “
Aeroelastic Instability in Transonic Fans
,”
J. Eng. Gas. Turbine. Power.
,
138
(
2
),
022604
.
5.
Lee
,
K.-B.
,
Wilson
,
M.
, and
Vahdati
,
M.
,
2017
, “
Numerical Study on Aeroelastic Instability for a Low-Speed Fan
,”
J. Turbomach.
,
139
(
7
),
071004
.
6.
Panovsky
,
J.
, and
Kielb
,
R. E.
,
1998
, “
A Design Method to Prevent Low Pressure Turbine Blade Flutter
,”
ASME 1998 International Gas Turbine and Aeroengine Congress and Exhibition
, American Society of Mechanical Engineers,
Stockholm, Sweden
,
June 2–5
, p.
V005T14A052
.
7.
Peeren
,
C.
, and
Vogeler
,
K.
,
2017
, “
Geometrical Modification of the Unsteady Pressure to Reduce Low-Pressure Turbine Flutter
,”
J. Turbomach.
,
139
(
9
),
091011
.
8.
Nipkau
,
J.
,
Power
,
B.
, and
Jordan
,
M.
,
2017
, “
Aeromechanical Design and Test of a Modern Highly Loaded Fan
,”
ASME Turbo Expo 2017: Turbomachinery Technical Conference and Exposition
, American Society of Mechanical Engineers,
Charlotte, NC
,
June 26–30
, p.
V02BT41A039
.
9.
Figaschewsky
,
F.
,
Kühhorn
,
A.
,
Beirow
,
B.
,
Nipkau
,
J.
,
Giersch
,
T.
, and
Power
,
B.
,
2017
, “
Design and Analysis of an Intentional Mistuning Experiment Reducing Flutter Susceptibility and Minimizing Forced Response of a Jet Engine Fan
,”
ASME Turbo Expo 2017: Turbomachinery Technical Conference and Exposition
, American Society of Mechanical Engineers,
Charlotte, NC
,
June 26–30
, p.
V07BT36A020
.
10.
Sayma
,
A. I.
,
Vahdati
,
M.
, and
Imregun
,
M.
,
2000
, “
An Integrated Non Linear Approach for Turbomachinery Forced Response Prediction, Part 1: Formulation
,”
J. Fluids. Struct.
,
14
(
1
), pp.
87
101
.
11.
Spalart
,
P. R.
, and
Allmaras
,
S. R.
,
1992
, “
A One-Equation Turbulence Model for Aerodynamic Flows
,” AIAA Paper No. 92-0439.
12.
Lee
,
K.-B.
,
Wilson
,
M.
, and
Vahdati
,
M.
,
2016
, “
Numerical Study on Aeroelastic Instability for a Low Speed Fan
,”
ASME Turbo Expo 2016: Turbomachinery Technical Conference and Exposition
,
Seoul, South Korea
,
June 13–17
, p.
V07BT34A006
.
13.
Vahdati
,
M.
,
Sayma
,
A.
,
Freeman
,
C.
, and
Imregun
,
M.
,
2005
, “
On the Use of Atmospheric Boundary Conditions for Axial-Flow Compressor Stall Simulations
,”
J. Turbomach.
,
127
(
2
), pp.
349
351
.
14.
Choi
,
M.
,
Smith
,
N. H.
, and
Vahdati
,
M.
,
2013
, “
Validation of Numerical Simulation for Rotating Stall in a Transonic Fan
,”
J. Turbomach.
,
135
(
2
), p.
021004
.
15.
Dodds
,
J.
, and
Vahdati
,
M.
,
2015
, “
Rotating Stall Observations in a High Speed Compressor - Part II: Numerical Study
,”
J. Turbomach.
,
137
(
5
), p.
051003
.
16.
Crivellini
,
A.
,
2016
, “
Assessment of a Sponge Layer as a Non-Reflective Boundary Treatment with Highly Accurate Gust-Airfoil Interaction Results
,”
Int. J. Comut. Fluid. Dyn.
,
30
(
2
), pp.
176
200
.
17.
Salles
,
L.
, and
Vahdati
,
M.
,
2016
, “
Comparison of Two Numerical Algorithms for Computing the Effects of Mistuning of fan Flutter
,”
ASME Turbo Expo 2016: Turbomachinery Technical Conference and Exposition
,
Seoul, South Korea
,
June 13–17
, p.
V07BT34A018
.
You do not currently have access to this content.