Modern low pressure turbines (LPT) are designed in order to fulfil a various number of requirements such as high endurance, low noise, high efficiency, low weight, and low fuel consumption. Regarding the reduction of the emitted noise, different designs of LPT exit guide vanes (aerodynamically and/or acoustically optimized) of the turbine exit casing (TEC) were tested, and their noise reduction capabilities and aerodynamic performance were evaluated. In particular, measurements of TEC-losses were performed, and differences in the losses were reported. Measurements were carried out in a one and a half stage subsonic turbine test facility at the engine relevant operating point approach. This work focuses on the study of the unsteady flow field downstream of an unshrouded LPT rotor. The influence on the upstream flow field of a TEC design including acoustically optimized vanes (inverse cut-off TEC) is investigated and compared with a second TEC configuration without vanes (Vaneless TEC), by means of fast response aerodynamic pressure probe (FRAPP) measurements. The second configuration served as a reference concerning the influence of turbine exit guide vanes (TEGVs) onto the upstream located LPT rotor. The interactions between the stator and rotor wakes, secondary flows, and the TEGVs potential effect are identified via modal decomposition according to the theory of Tyler and Sofrin. The main structures constituting the unsteady flow field are detected, and the role of the major interaction effects in the loss generation mechanism and in the acoustic emission is analyzed. This study based on the modal analysis of the unsteady flow field offers new insight into the main interaction mechanisms and their importance in the assessment of the aerodynamic and aeroelastic performance of modern LPT exit casings.

References

References
1.
Binder
,
A.
,
Förster
,
W.
,
Kruse
,
H.
, and
Rogge
,
H.
,
1985
, “
An Experimental Investigation Into the Effect of Wakes on the Unsteady Turbine Rotor Flow
,”
ASME J. Eng. Gas Turbines Power
,
107
(
2
), pp.
458
465
.
2.
Sharma
,
O. P.
,
Butler
,
T. L.
,
Joslyn
,
H. D.
, and
Dring
,
R. P.
,
1985
, “
Three-Dimensional Unsteady Flow in an Axial Flow Turbine
,”
AIAA J. Propul. Power
,
1
(
1
), pp.
29
38
.
3.
Matsunuma
,
T.
,
2006
, “
Unsteady Flow Field of an Axial-Flow Turbine Rotor at a Low Reynolds Number
,”
ASME J. Turbomach.
,
129
(
2
), pp.
360
371
.
4.
Tyler
,
J. M.
, and
Sofrin
,
T. G.
,
1962
, “
Axial Flow Compressor Noise Studies
,”
SAE Trans.
,
70
, pp.
309
332
.https://www.jstor.org/stable/44469492
5.
Lengani
,
D.
,
Paradiso
,
B.
,
Marn
,
A.
, and
Göttlich
,
E.
,
2012
, “
Identification of Spinning Mode in the Unsteady Flow Field of a Low Pressure Turbine
,”
ASME J. Turbomach.
,
134
(
5
), p.
051032
.
6.
Lengani
,
D.
,
Selic
,
T.
,
Spataro
,
R.
,
Marn
,
A.
, and
Göttlich
,
E.
,
2012
, “
Analysis of the Unsteady Flow Field in Turbines by Means of Modal Decomposition
,”
ASME
Paper No. GT2012-68582.
7.
Moser
,
M.
,
Tapken
,
U.
,
Enghardt
,
L.
, and
Neuhaus
,
L.
,
2009
, “
An Investigation of LP-Turbine Blade/-Vane Interaction Noise: Measurements in a 1.5 Stage Rig
,”
IMechE J. Power Energy
,
223
(
6
), pp.
687
695
.
8.
Zerobin
,
S.
,
Bauinger
,
S.
,
Marn
,
A.
,
Peters
,
A.
,
Heitmeir
,
F.
, and
Göttlich
,
E.
,
2017
, “
The Unsteady Flow Field of a Purged High Pressure Turbine Based on Mode Detection
,”
ASME
Paper No. GT2017-63619.
9.
Schönleitner
,
F.
,
Selic
,
T.
,
Schitter
,
C.
,
Heitmeir
,
F.
, and
Marn
,
A.
,
2016
, “
Experimental Investigation of the Upstream Effect of Different Low Pressure Turbine Exit Guide Vane Designs on Rotor Blade Vibration
,”
ASME
Paper No. GT2016-56067.
10.
Selic
,
T.
,
Marn
,
A.
,
Schönleitner
,
F.
,
Hoeger
,
M.
,
Broszat
,
D.
, and
Heitmeir
,
F.
,
2015
, “
Comparison of an Acoustically Optimized and an Aerodynamically Optimized Exit Guide Vane
,” 11th European Conference on Turbomachinery Fluid dynamics and Thermodynamics (
ETC
), Madrid, Spain, Mar. 23–27.http://www.euroturbo.eu/paper/ETC2015-158.pdf
11.
Marn
,
A.
,
Selic
,
T.
,
Schönleitner
,
F.
, and
Zerobin
,
S.
,
2015
, “
Acoustic Comparison of Different Turbine Exit Guide Vane Designs—Part 2: Experimental Analysis
,”
AIAA
Paper No. 2015-2823.
12.
Persico
,
G.
,
Gaetani
,
P.
, and
Guardone
,
A.
,
2005
, “
Design and Analysis of New Concept Fast-Response Pressure Probes
,”
Meas. Sci. Technol.
,
16
(
9
), pp.
1741
1750.
13.
Lengani
,
D.
,
Paradiso
,
B.
, and
Marn
,
A.
,
2012
, “
A Method for the Determination of Turbulence Intensity by Means of a Fast Response Pressure Probe and Its Application in a LP Turbine
,”
J. Therm. Sci.
,
21
(
1
), pp. 21–31.
14.
Camp
,
T. R.
, and
Shin
,
H. W.
,
1995
, “
Turbulence Intensity and Length Scale Measurements in Multistage Compressors
,”
ASME J. Turbomach.
,
117
(
1
), pp.
38
46
.
15.
Morfey
,
C.
,
1971
, “
Sound Transmission and Generation in Ducts With Flow
,”
J. Sound Vib.
,
14
(
1
), pp.
37
55
.
16.
Lengani
,
D.
,
Santner
,
C.
,
Spataro
,
R.
, and
Göttlich
,
E.
,
2012
, “
Analysis Tools for the Unsteady Interactions in a Counter-Rotating Two-Spool Turbine Rig
,”
Exp. Therm. Fluid Sci.
,
42
, pp.
248
257
.
17.
Bindon
,
J. P.
,
1989
, “
The Measurement and Formation of Tip Leakage Loss
,”
ASME J. Turbomach.
,
111
(
3
), pp.
257
263
.
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