High cycle fatigue (HCF) due to unforeseen excitation frequencies, underestimated force magnitudes, or a combination of both causes control-stage failures for steam turbine stakeholders. This paper provides an extended design criteria toolbox, as well as validation data, for control-stage design based on experimental data to reduce HCF incidents in partial-admission turbines. The upstream rotor in a two-stage air test turbine is instrumented with pressure transducers and strain gauges. Admission degrees extend from 28.6% to 100%, as one or two admission arcs are simulated by blocking segmental arcs immediately upstream of the first stator vanes with aerodynamically shaped filling blocks. Sweeps across a speed range of 50%–105% of design speed are performed at a constant turbine pressure ratio during simultaneous high-speed acquisition. A forced-response analysis is performed and results presented in Campbell diagrams. Partial admission creates a large number of low-engine-order forced responses because of the blockage, pumping, loading, and unloading processes. Combinations of the number of rotor blades and low-engine-order excitations are the principal sources of forced-response vibrations for the turbine studied here. Altering the stator and/or rotor pitches changes the excitation pattern. We observed that a relationship between the circumferential lengths of the admitted and nonadmitted arcs dictates the excitation forces and may serve as a design parameter.

References

References
1.
Stodola
,
A.
,
1927
,
Steam and Gas Turbines
, Vol. I (
L.C.
Loewenstein
, trans.),
McGraw-Hill Book Co., Inc.
, Reprinted in 1945 by P. Smith.,
Magnolia, MA
.
2.
Ohlsson
,
G. O.
,
1962
, “
Partial-Admission Turbines
,”
J. Aerosp. Sci.
,
29
(
9
), pp.
1017
1028
.
3.
Traupel
,
W.
,
1977
,
Thermische Turbomaschinen
, Vol. 2,
3rd ed
., Springer-Verlag, Berlin.
4.
Boulbin
,
F.
,
Penneron
,
N.
,
Kermarec
,
J.
, and
Pluviose
,
M.
,
1992
, “
Turbine Blade Forces due to Partial Admission
,”
Rev. Fran. Mec.
,
1992-3
, pp.
203
208
.
5.
He
,
L.
,
1997
, “
Computation of Unsteady Flow through Steam Turbine Blade Rows at Partial Admission
,”
P. I. Mech. Eng. A-J Pow.
,
211
(
3
), pp.
297
305
.10.1243/0957650971537105
6.
Hushmandi
,
B. N.
,
Fridh
,
J.
, and
Fransson
,
T.
,
2011
, “
Unsteady Forces of Rotor Blades in Full– and Partial admission Turbines
,”
ASME J. Turbomach.
,
133
(
4
), p.
041017
10.1115/1.4002408.
7.
Fridh
,
J.
,
Bunkute
,
B.
,
Fakhrai
,
R.
, and
Fransson
,
T.
,
2004
, “
An Experimental Study on Partial Admission in a Two-Stage Axial Air Test Turbine With Numerical Comparisons
,”
Proceedings of ASME Turbo Expo 2004
, Paper No. GT 2004-53774.
8.
Fridh
,
J.
,
Wikström
,
R.
, and
Fransson
,
T.
,
2007
, “
Dynamic Features of Partial Admission: Outcomes from Rotating Measurements
,”
Proceedings of 7th European Conference on Turbomachinery
,
Fluid Dynamics and Thermodynamics
, pp.
451
462
.
9.
Fridh
,
J.
,
Fransson
,
T.
,
Andersson
,
N-E.
, and
Magnusson
,
P.
,
2006
, “
Redundant Rotating Measurements in an Axial Cold Flow Test Turbine – Development and Procedure
,”
Proceedings of the XVIII Symposium on Measuring Techniques in Turbomachinery
,
Transonic and Supersonic Flow in Cascades and Turbomachines
,
Thessaloniki
,
Greece
, September, Paper No. 18MTT09.
10.
Ainsworth
,
R. W.
,
Miller
,
R. J.
,
Moss
,
R. W.
, and
Thorpe
,
S. J.
,
2000
, “
Unsteady Pressure Measurements
,”
Meas. Sci. Tech.
,
11
(
1
), pp.
1055
1076
.10.1088/0957-0233/11/7/319
11.
Kurtz
,
A. D.
,
Ainsworth
,
R. W.
,
Thorpe
,
S. J.
, and
Ned
,
A.
,
2000
, “
Acceleration-Insensitive Semiconductor Pressure Sensors for High Bandwidth Measurements on Rotating Turbine Blades
,”
Proceedings of the 15th Symposium on Measuring Techniques for Transonic and Supersonic Flow in Cascade and Turbomachines
,
Florence
, September.
12.
Wildheim
,
S. J.
,
1979
, “
Excitation of Rotationally Periodic Structures
,”
ASME J. Appl. Mech.
,
46
(
4
), pp.
878
882
.10.1115/1.3424671
13.
Wildheim
,
S. J.
,
1980
, “
Natural Frequencies of Rotating Bladed Discs using Clamped-Free Blade Modes
,” Internal report, LiTH-IKP-R-169,
The Institute of Technology at Linköping University
,
Linköping, Sweden
.
14.
Isakson
,
G.
, and
Eisley
,
J. G.
,
1964
, “
Natural Frequencies in Coupled Bending and Torsion of Twisted Rotating and Non-Rotating Blades
,” NASA CR-65.
15.
Imregun
,
M.
,
1999
, “
Advanced Topics in Bladed Disk Vibration & Basics of Rotor Vibration
,” Lecture notes, VKI Lecture series – Aeroelasticity in Axial Flow Turbines, Rhode-Saint-Genése, Belgium, May 1999.
16.
Pigott
,
R.
,
1980
, “
Turbine Blade Vibration due to Partial Admission
,”
Int. J. Mech. Sci.
,
22
(
1
), pp.
247
264
.10.1016/0020-7403(80)90039-9
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