The inside-out ceramic turbine (ICT) is a promising concept to increase turbine inlet temperatures in microturbines by integrating individual monolithic ceramic. This architecture uses a carbon–polymer composite rim to support the blades mainly in compression. High tangential velocities lead to elevated radial displacement of the rim, and therefore, the rotor hub needs to have sufficient compliance to follow this radial displacement. However, the rotordynamics of a flexible hub is not widely understood. This paper presents the rotordynamic analysis of a highly flexible hub for an ICT architecture. Finite element modeling (FEM) is used to design a simplified turbine prototype that maximizes the hub flexibility to explore the limits of the concept. The rotordynamics behavior of the highly flexible hub is measured by spinning a 171-mm diameter prototype up to 49 krpm. This paper highlights three principal challenges of this particular rotordynamics. First, critical speeds mode shape becomes highly coupled with bearings displacement, shaft bending, and hub deformation. At high-speed, the hub deforms out of phase with the shaft, which can cause high stresses in the hub. Second, the angular position between unbalance masses of the flexible hub and the composite rim changes the unbalance response significantly. Finally, vibration causes high stresses in the hub, due to the relative displacement between the composite rim and the shaft, which could lead to failure of the hub. Nevertheless, the rotordynamics of an ICT configuration is manageable as long as the vibration-induced stress in the hub is kept under its limit.

References

References
1.
Rodgers
,
C.
,
2003
, “
Some Effects of Size on the Performances of Small Gas Turbines
,”
ASME
Paper No. GT2003-38027.
2.
Coty
,
P. J.
,
1983
, “
Compression Structured Ceramic Turbine Rotor Concept
,”
Ceramics for High-Performance Applications III
,
E. M.
Lenoe
,
R. N.
Katz
, and
J. J.
Burke
, eds.,
Springer
,
New York
, pp.
427
441
.
3.
Landry
,
C.
,
Dubois
,
P. K.
,
Courtois
,
N.
,
Charron
,
F.
,
Picard
,
M.
, and
Plante
,
J.-S.
,
2016
, “
Development of an Inside-Out Ceramic Turbine
,”
ASME
Paper No. GT2016-57041.
4.
Kochendörfer
,
R.
,
1979
, “
Compression Loaded Ceramic Turbine Rotor
,”
AGARD Conference Proceedings
, Monterey, CA, Oct. 16–17, p. 22.
5.
Stoffer
,
L. J.
,
1979
, “
Novel Ceramic Turbine Rotor Concept
,” General Electric Company, Cincinnati, OH, Technical Report No.
AFAPL-TR-79-2074
.
6.
Kim
,
S. J.
,
Hayat
,
K.
,
Nasir
,
S. U.
, and
Ha
,
S. K.
,
2014
, “
Design and Fabrication of Hybrid Composite Hubs for a Multi-Rim Flywheel Energy Storage System
,”
Compos. Struct.
,
107
, pp.
19
29
.
7.
Ha
,
S. K.
,
Kim
,
M. H.
,
Han
,
S. C.
, and
Sung
,
T.-H.
,
2006
, “
Design and Spin Test of a Hybrid Composite Flywheel Rotor With a Split Type Hub
,”
J. Compos. Mater.
,
40
(
23
), pp.
2113
2130
.
8.
Moreira
,
A.
, and
Flowers
,
G.
,
2005
, “
The Influence of Internal Damping on the Rotordynamic Stability of a Flywheel Rotor With Flexible Hub
,”
ASME
Paper No. DETC2005-84195.
9.
Flowers
,
G. T.
,
1996
, “
Modelling of an Elastic Disk With Finite Hub Motions and Small Elastic Vibrations With Application to Rotordynamics
,”
ASME J. Vib. Acoust.
,
118
(
1
), pp.
10
15
.
10.
Flowers
,
G. T.
, and
Ryan
,
S. G.
,
1991
, “
Development of a Set of Equations for Incorporating Disk Flexibility Effects in Rotordynamical Analyses
,”
ASME
Paper No. 91-GT-075.
11.
Ehrich
,
F.
, and
Childs
,
D.
,
1984
, “
Self-Excited Vibration in High-Performance Turbomachinery
,”
Mech. Eng.
,
106
(
5
), pp.
66
79
.
12.
Nguyen-Schäfer
,
H.
,
2012
,
Rotordynamics of Automotive Turbochargers
, Springer-Verlag, Berlin.
13.
San Andrés
,
L.
,
2012
, “
Damping and Inertia Coefficients for Two Open Ends Squeeze Film Dampers With a Central Groove: Measurements and Predictions
,”
ASME J. Eng. Gas Turbines Power
,
134
(
10
), p.
102506
.
14.
Zeidan
,
F. Y.
,
San Andres
,
L.
, and
Vance
,
J. M.
,
1996
, “
Design and Application of Squeeze Film Dampers in Rotating Machinery
,”
25th Turbomachinery Symposium
, Houston, TX, Sept. 17–19, pp.
169
188
.
15.
Barrett
,
L. E.
, and
Gunter
,
E. J.
,
1975
, “
Steady-State and Transient Analysis of a Squeeze Film Damper Bearing for Rotor Stability
,” National Aeronautics and Space Administration, Washington, DC, Report No.
NASA CR-2548
.
16.
Greenhill
,
L. M.
, and
Cornejo
,
G. A.
,
1995
, “
Critical Speeds Resulting From Unbalance Excitation of Backward Whirl Modes
,”
ASME Design Engineering Technical Conference. Part B
, Boston, MA, Sept. 17–20, pp.
991
1000
.
17.
Maalouf
,
M. G.
,
2007
, “
Slow Speed Vibration Signal Analysis: If You Can't Do It Slow, You Can't Do It Fast
,”
ASME
Paper No. GT2007-28252.
You do not currently have access to this content.