This paper presents the work on part-speed fan flutter due to acoustic reflections from the intake, commonly called “flutter bite.” A simple model for the prediction of the flutter bite is presented. In a previous work by the authors, it was shown that the acoustic effects of the intake are very important and need to be considered during the design of a fan blade. It was also shown that the contribution to blade aerodamping due to blade motion (for the isolated rotor in an infinitely long duct) and intake acoustics is independent and can be analyzed separately. The acoustic reflections from the intake change the damping of the blade by modifying the phase and amplitude of the unsteady pressure at the leading edge of the fan. It will be shown in the paper that, for a given intake, the phase and amplitude of the reflected acoustic waves can be evaluated analytically based on established theories independent of the fan design. The proposed model requires only the design intent of the fan blade and the geometry of the intake, which are available in the early design stages of a new engine, and can predict the operating conditions at which fan flutter is likely to occur.

References

References
1.
Vahdati
,
M.
,
Simpson
,
G.
, and
Imregun
,
M.
,
2011
, “
Mechanisms for Wide-Chord Fan Blade Flutter
,”
ASME J. Turbomach.
,
133
(
4
), p.
041029
.
2.
Vahdati
,
M.
,
Smith
,
N. H. S.
, and
Zhao
,
F.
,
2015
, “
Influence of Intake on Fan Blade Flutter
,”
ASME J. Turbomach.
,
137
(
8
), p.
081002
.
3.
Rice
,
E.
,
Heidmann
,
M.
, and
Sofrin
,
T.
,
1979
, “
Modal Propagation Angles in a Cylindrical Duct With Flow and Their Relation to Sound Radiation
,”
AIAA
Paper No. 79-0183.
4.
Rienstra
,
S.
,
1984
, “
Acoustic Radiation From a Semi-Infinite Annular Duct in a Uniform Subsonic Mean Flow
,”
J. Sound Vib.
,
94
(
2
), pp.
267
288
.
5.
Tyler
,
J. M.
, and
Sofrin
,
T. G.
,
1962
, “
Axial Flow Compressor Noise Studies
,”
Trans. Soc. Automot. Eng.
,
70
, pp.
309
332
.
6.
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
.
7.
Swanson
,
R.
, and
Turkel
,
E.
,
1992
, “
On Central-Difference and Upwind Schemes
,”
J. Comput. Phys.
,
101
(
2
), pp.
292
306
.
8.
Spalart
,
P.
, and
Allmaras
,
S.
,
1992
, “
A One-Equation Turbulence Model for Aerodynamic Flows
,”
AIAA
Paper No. 92-0439.
9.
Choi
,
M.
,
Smith
,
N. H. S.
, and
Vahdati
,
M.
,
2013
, “
Validation of Numerical Simulation for Rotating Stall in a Transonic Fan
,”
ASME J. Turbomach.
,
135
(
2
), p.
021004
.
10.
Dodds
,
J.
, and
Vahdati
,
M.
,
2014
, “
Rotating Stall Observations in a High Speed Compressor Part II: Numerical Study
,”
ASME J. Turbomach.
,
137
(
5
), p.
051003
.
11.
Giles
,
M.
,
1990
, “
Non-Reflecting Boundary Conditions for the Euler Equations
,”
AIAA J.
,
28
(
12
), pp.
2050
2058
.
12.
Wiener
,
N.
, and
Hopf
,
E.
,
1931
, “
Über eine Klasse singulärer Integralgleichungen
,”
Sem-Ber. Preuss. Akad. Wiss. Berlin
,
30/32
, pp.
696
706
.
13.
Moinier
,
P.
, and
Giles
,
M. B.
,
2005
, “
Eigenmode Analysis for Turbomachinery Applications
,”
J. Propul. Power
,
21
(
6
), pp.
973
978
.
14.
Rienstra
,
S. W.
,
1999
, “
Sound transmission in slowly varying circular and annular lined ducts with flow
,”
J. Fluid Mech.
,
380
, pp.
279
296
.
15.
Cooper
,
A. J.
, and
Peake
,
N.
,
2001
, “
Propagation of Unsteady Disturbances in a Slowly Varying Duct With Mean Swirling Flow
,”
J. Fluid Mech.
,
445
, pp.
207
234
.
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