Abstract

This paper investigates the three dimensionality of the unsteady flow responsible for stall flutter instability. Nonlinear unsteady Reynolds-averaged Navier–Stokes (RANS) computations are used to predict the aeroelastic behavior of a fan blade at part speed. Flutter is experienced by the blades at low mass flow for the first flap mode at nodal diameter 2. The maximal energy exchange is located near the tip of the blade, at 90% span. The modeshape is radially decomposed to investigate the main source of instability. This decomposition method is validated for the first time in 3D using a time-marching nonlinear solver. The source of stall flutter is finally found at 65% span where the local vibration induces an unstable oscillation of the shock-wave of large amplitude. This demonstrates that the radial migration of the pressure fluctuations must be taken into account to predict stall flutter.

References

1.
Zhao
,
F.
,
Smith
,
N.
, and
Vahdati
,
M.
,
2017
, “
A Simple Model for Identifying the Flutter Bite of Fan Blades
,”
ASME J. Turbomach.
,
139
(
7
), p.
071003
. 10.1115/1.4035567
2.
Aotsuka
,
M.
, and
Murooka
,
T.
,
2014
, “
Numerical Analysis of Fan Transonic Stall Flutter
,”
ASME Turbo Expo 2014: Turbine Technical Conference and Exposition
,
Düsseldorf, Germany
,
June 16–20
,
American Society of Mechanical Engineers
, p.
V07BT35A020
.
3.
Vahdati
,
M.
, and
Cumpsty
,
N.
,
2016
, “
Aeroelastic Instability in Transonic Fans
,”
ASME J. Eng. Gas Turbines Power
,
138
(
2
), p.
022604
. 10.1115/1.4031225
4.
Ferrand
,
P.
,
1984
, “
Linearized Theory of the Choked Flow in an Annular Oscillating Cascade
,”
Unsteady Aerodynamics and Aeroelasticity of Turbomachines and Propellers
,
Cambridge, England
,
Sept.
, pp.
41
52
.
5.
Rendu
,
Q.
,
Aubert
,
S.
, and
Ferrand
,
P.
,
2017
, “
Influence of Reduced Frequency on Choke Flutter in Transonic UHBR Fan
,”
International Forum on Aeroelasticity and Structural Dynamics
,
Como, Italy
,
June 25–28
, pp.
1812
1826
.
6.
Spalart
,
P.
, and
Allmaras
,
S.
,
1992
, “
A One-Equation Turbulence Model for Aerodynamic Flows
,”
30th Aerospace Sciences Meeting
,
Reno, NV
,
Jan. 6
, p.
439
.
7.
Sayma
,
A.
,
Vahdati
,
M.
, and
Imregun
,
M.
,
2000
, “
An Integrated Nonlinear Approach for Turbomachinery Forced Response Prediction. Part I: Formulation
,”
J. Fluids Struct.
,
14
(
1
), pp.
87
101
. 10.1006/jfls.1999.0253
8.
Stapelfeldt
,
S.
, and
Di Mare
,
L.
,
2015
, “
Reduced Passage Method for Multirow Forced Response Computations
,”
AIAA J.
,
53
(
10
), pp.
3049
3062
.
9.
Vahdati
,
M.
,
Simpson
,
G.
, and
Imregun
,
M.
,
2011
, “
Mechanisms for Wide-Chord Fan Blade Flutter
,”
ASME J. Turbomach.
,
133
(
4
), p.
041029
. 10.1115/1.4001233
10.
Rendu
,
Q.
,
Rozenberg
,
Y.
,
Aubert
,
S.
, and
Ferrand
,
P.
,
2017
, “
Influence of Acoustic Blockage on Flutter Instability in a Transonic Nozzle
,”
ASME J. Turbomach.
,
140
(
2
), p.
021004
. 10.1115/1.4038279
11.
Atassi
,
H.
,
Fang
,
J.
, and
Ferrand
,
P.
,
1995
, “
Acoustic Blockage Effects in Unsteady Transonic Nozzle and Cascade Flows
,”
33rd AIAA Aerospace Sciences Meeting
,
Reno, NV
,
Jan. 9–12
, p.
303
.
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