The growing pressure to reduce fuel consumption and cut emissions has triggered renewed interest in contra-rotating open rotor (CROR) technologies. One of their potential issues is self-excited or forced vibration of the unducted, light-weight, highly swept blades. This paper presents a numerical study into the flutter behavior of a CROR rig at take-off conditions. The study presented in this paper aimed to validate the numerical approach and provide insights into the flutter mechanisms of the open rotor under investigation. For the initial validation, pressure profiles and thrust coefficients from steady-state mixing plane calculations were compared against rig measurements. A full domain unsteady analysis predicted front rotor instability at low advance ratios. Flutter occurred in the first torsional mode in 0 and 1 nodal diameter (ND) which agreed with experimental observations. Subsequent unsteady computations focused on the isolated front rotor and first torsional mode. The flow field and aerodynamic damping over a range of advance ratios were studied. It was found that minimum aerodynamic damping occurred at low advance ratios when the flow was highly three-dimensional on the suction side. A correlation between the quasi-steady loading on the blade and aeroelastic stability was made and related to the numerical results. The effects of variations in frequency were then investigated by linking local aerodynamic damping to the unsteady pressure on the blade surface.

References

References
1.
Ricouard
,
J.
,
Julliard
,
E.
,
Omaïs
,
M.
, and
Regnier
,
V.
,
2010
, “
Installation Effects on Contra-Rotating Open Rotor Noise
,”
AIAA/CEAS Aeroacoustics Conference
,
AIAA
Paper No. 2010-3795.
2.
Parry
,
A.
,
Kingan
,
M.
, and
Tester
,
B.
,
2011
, “
Relative Importance of Open Rotor Tone and Broadband Noise Sources
,”
AIAA/CEAS Aeroacoustics Conference
,
AIAA
Paper No. 2011-2763.
3.
Kingan
,
M.
,
Ecoule
,
C.
,
Parry
,
A.
, and
Britchford
,
K.
,
2014
, “
Analysis of Advanced Open Rotor Noise Measurements
,”
AIAA/CEAS Aeroacoustics Conference
,
AIAA
Paper No. 2014-2745.
4.
Clark
,
S.
,
Kielb
,
R.
, and
Hall
,
K.
, “
The Effect of Mass Ratio, Frequency Separation and Solidity on Multi-Mode Fan Flutter
,”
12th International Symposium on Unsteady Aerodynamics, Aeroacoustics and Aeroelasticity of Turbomachines, ISUAAAT
, Paper No. I12-S2-3.
5.
August
,
R.
, and
Kaza
,
K.
,
1988
, “
Vibration, Performance, Flutter and Forced Response Characteristics of a Large-Scale Propfan and Its Aeroelastic Model
,” Technical Report No. NASA-TM-101322.
6.
Mehmed
,
O.
,
Kaza
,
K.
,
Lubomski
,
J.
, and
Kielb
,
R. E.
,
1982
, “
Bending–Torsion Flutter of a Highly Swept Advanced Turboprop
,”
Technical Report No. NASA-TM-82975
.
7.
Crawley
,
E. F.
, and
Ducharme
,
E. H.
,
1990
, “
Parametric Trends in the Flutter of Advanced Turboprops
,”
ASME J. Turbomach.
,
112
(
4
), pp.
741
750
.
8.
Hoff
,
G.
,
1990
, “
Experimental Performance and Acoustic Investigation of Modern Counterrotating Blade Concepts
,” GE Aircraft Engines, Advanced Technology Operations,
NASA Contractor Report 185158
.
9.
Stapelfeldt
,
S.
,
Parry
,
T.
, and
Vahdati
,
M.
,
2015
, “
Validation of Time-Domain Single-Passage Methods for the Unsteady Simulation of a Contra-Rotating Open Rotor
,”
Proc. Inst. Mech. Eng.
, Part A,
229
(
5
), pp.
443
453
.
10.
Vahdati
,
M.
,
Simpson
,
G.
, and
Imregun
,
M.
,
2011
, “
Mechanisms for Wide-Chord Fan Blade Flutter
,”
ASME J. Eng. Gas Turbines Power
,
133
(
4
), p.
041029
.
11.
Vahdati
,
M.
, and
Cumpsty
,
N.
,
2012
, “
The Mechanism of Aeroelastic Instability in Transonic Fans
,”
13th International Symposium on Unsteady Aerodynamics, Aeroacoustics and Aeroelasticity of Turbomachines, ISUAAAT
, Paper No. I13-I-5.
12.
Spalart
,
P. R.
, and
Allmaras
,
S. R.
,
1992
, “
A One-Equation Turbulence Model for Aerodynamic Flows
,”
AIAA
Paper No. 92-0439.
13.
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
.
14.
Sbardella
,
L.
,
Sayma
,
A.
, and
Imregun
,
M.
,
2000
, “
Semi-Structured Meshes for Axial Turbomachinery Blades
,”
Int. J. Numer. Methods Fluids
,
32
(
5
), pp.
569
584
.
15.
Zachariadis
,
A.
,
Hall
,
C.
, and
Parry
,
A.
,
2011
, “
Contra-Rotating Open Rotor Operation for Improved Aerodynamics and Noise at Take-Off
,”
ASME Turbo Expo
, pp.
973
983
.
16.
Riemann
,
B.
,
1860
,
Über die Fortpflanzung ebener Luftwellen von endlicher Schwingungsweiter
, Vol.
8
,
Abhandlungen der Königlichen Gesellschaft der Wissenschaften zu Göttingen
,
Göttingen, Germany
.
17.
Groeneweg
,
J.
, and
Bober
,
L.
,
1988
, “
NASA Advanced Propeller Research
,”
Technical Report No. NASA-TM-101361
.
You do not currently have access to this content.