Results from scale-model experiments and industrial gas turbine tests show that strut vortex shedding in an annular exhaust diffuser can effectively be modified by adding tapered chord to the struts. The struts are bluff bodies at full-speed, no-load conditions, when inlet swirl is close to 60 deg. Data from wind tunnel tests show that wake Strouhal number is 0.47, larger than that expected for an isolated cylinder wake. This value of Strouhal number agrees with those measured in full-scale exhaust diffusers. Wind tunnel tests showed that a strut with tapered chord most effectively reduced wake amplitudes and shifted shedding frequency. The tapered strut was also effective in reducing shedding amplitude in a scale-model diffuser. Finally, gas turbine tests employing a tapered strut showed significant reductions in unsteady pressure and noise. A major benefit of strut taper is a reduction of noise by uncoupling of vortex shedding from acoustic resonant response.

Issue Section:
Research Papers
Topics:
Diffusers, Exhaust systems, Vortex shedding, Struts (Engineering), Wakes, Chords (Trusses), Noise (Sound), Wind tunnels, Acoustics, Cylinders, Gas turbines, Industrial gases, Pressure, Stress, Turbines, Resonance
1.
Alford, J. S., 1966, “Protecting Turbomachinery From Unstable and Oscillatory Flows,” ASME Paper No. 66-WA/GT-13, pp. 145–166.
2.
Cenedese, A., Cerri, G. and Iannetta, S., 1981, “LDV Analysis of Wakes Behind Circular Cylinders and Airfoils,” Meccanica, Dec., pp. 220–231.
3.
Cimbala
J. M.
, and
Garg
S.
,
1991
, “
Flow in the Wake of a Freely Rotatable Cylinder With Splitter Plate
,”
AIAA Journal
, Vol.
29
(
6
), pp.
1001
–
1003
.
4.
Fung, Y. C., 1955, An Introduction to the Theory of Aeroelasticity, Wiley, London.
5.
Gulati, A., 1990, “Passive Control of Combustion-Induced Instabilities,” General Electric Company—CRD Report 90CRD093.
6.
Higuchi
H.
, and
Takahashi
F.
,
1989
, “
Flow Past Two-Dimensional Ribbon Parachute Models
,”
J. Aircraft
, Vol.
26
(
7
), pp.
641
–
649
.
7.
Lesage
F.
, and
Gartshore
I. S.
,
1987
, “
A Method of Reducing Drag and Fluctuating Side Force on Bluff Bodies
,”
Journal of Wind Engineering and Industrial Aerodynamics
, Vol.
25
, pp.
229
–
245
.
8.
McLachlan, B. G., and Karamcheti, K., 1985, “An Experimental Study of Airfoil-Spoiler Aerodynamics,” NASA-CR-177328.
9.
Parker
R.
, and
Pryce
D. C.
,
1974
, “
Wake Excited Resonances in an Annular Cascade: An Experimental Investigation
,”
Journal of Sound and Vibration
, Vol.
37
(
1
), pp.
247
–
261
.
10.
Parker
R.
, and
Stoneman
S. A. T.
,
1989
, “
The Excitation and Consequences of Acoustic Resonances in Enclosed Fluid Flow Around Solid Bodies
,”
Proc. Instn. Mech. Engrs
, Vol.
203
, pp.
9
–
19
.
11.
Rizk
M. A.
, and
Seymour
D. F.
,
1964
, “
Investigations Into the Failure of Gas Circulators and Circuit Components at Hinkley Point Nuclear Power Station
,”
Proc. Instn Mech. Engrs
, Vol.
179
(1), No.
21
, pp.
627
–
703
.
12.
Roshko
A.
,
1955
, “
On the Wake and Drag of Bluff Bodies
,”
Journal of Aeronautical Sciences
, Vol.
22
(
1
), pp.
124
–
132
.
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