Experiments in a refractive index-matched axial turbomachine facility show that semicircular skewed axial casing grooves (ACGs) reduce the stall flowrate by 40% but cause a 2.4% decrease in the maximum efficiency. Aiming to elucidate mechanism that might cause the reduced efficiency, stereo-PIV measurements examine the impact of the ACGs on the flow structure and turbulence in the tip region near the best efficiency point (BEP), and compare them to those occurring without grooves and at low flowrates. Results show that the periodic inflow into the groove peaks when the rotor blade pressure side (PS) overlaps with the downstream end of the groove, but diminishes when this end faces the suction side (SS). Entrainment of the PS boundary layer and its vorticity generates a vortical loop at the entrance to the groove, and a “discontinuity” in the tip leakage vortex (TLV) trajectory. During exposure to the SS, the backward tip leakage flow separates at the entrance to the groove, generating a counter-rotating circumferential “corner vortex,” which the TLV entrains into the passage at high flowrates. Interactions among these structures enlarge the TLV and create a broad area with secondary flows and elevated turbulence near the groove's downstream corner. A growing shear layer with weaker turbulence also originates from the upstream corner. The groove also increases the flow angle upstream of the blade tip and varies it periodically. Accordingly, the circulation shed from the blade tip and strength of leakage flow increase near the blade leading edge (LE).

References

References
1.
Moore
,
R. D.
,
Kovich
,
G.
, and
Blade
,
R. J.
,
1971
, “
Effect of Casing Treatment on Overall and Blade Element Performance of a Compressor Rotor
,” National Aeronautics and Space Administration, Washington, DC, Report No. NASA-TN-D-6538, E-6119.
2.
Osborn
,
W. M.
,
Lewis
,
G. W. J.
, and
Heidelberg
,
L. J.
,
1971
, “
Effect of Several Porous Casing Treatments on Stall Limit and on Overall Performance of an Axial-Flow Compressor Rotor
,” NASA, Washington, DC, Report No. NASA-TN-D-6537, E-5973.
3.
Takata
,
H.
, and
Tsukuda
,
Y.
,
1977
, “
Stall Margin Improvement by Casing Treatment—Its Mechanism and Effectiveness
,”
ASME J. Eng. Power
,
99
(
1
), pp.
121
133
.
4.
Smith
,
G. D. J.
, and
Cumpsty
,
N. A.
,
1984
, “
Flow Phenomena in Compressor Casing Treatment
,”
ASME J. Eng. Gas Turbines Power
,
106
(
3
), pp.
532
541
.
5.
Brandstetter
,
C.
,
Kegalj
,
M.
,
Wartzek
,
F.
,
Heinichen
,
F.
, and
Schiffer
,
H.-P.
,
2014
, “
Stereo PIV Measurement of Flow Structures underneath an Axial-Slot Casing Treatment on a One and a Half Stage Transonic Compressor
,”
17th International Symposium on Applications of Laser Techniques to Fluid Mechanics
, pp.
1
18
.
6.
Crook
,
A. J.
,
Greitzer
,
E. M.
,
Tan
,
C. S.
, and
Adamczyk
,
J. J.
,
1993
, “
Numerical Simulation of Compressor End wall and Casing Treatment Flow Phenomena
,”
ASME J. Turbomach.
,
115
(
3
), pp.
501
512
.
7.
Fujita
,
H.
, and
Takata
,
H.
,
1984
, “
A Study on Configurations of Casing Treatment for Axial Flow Compressors
,”
Bull. JSME
,
27
(
230
), pp.
1675
1681
.
8.
Müller
,
M. W.
,
Schiffer
,
H.-P.
,
Voges
,
M.
, and
Hah
,
C.
,
2011
, “
Investigation of Passage Flow Features in a Transonic Compressor Rotor
,”
ASME
Paper No. GT2011-45364.
9.
Wilke
,
I.
, and
Kau
,
H.-P.
,
2004
, “
A Numerical Investigation of the Flow Mechanisms in a High Pressure Compressor Front Stage With Axial Slots
,”
ASME J. Turbomach.
,
126
(
3
), pp.
339
349
.
10.
Seitz
,
P. A.
,
1999
, “
Casing Treatment for Axial Flow Compressors
,” Ph.D. thesis, University of Cambridge, Cambridge, UK.
11.
Beheshti
,
B. H.
,
Teixeira
,
J. A.
,
Ivey
,
P. C.
,
Ghorbanian
,
K.
, and
Farhanieh
,
B.
,
2004
, “
Parametric Study of Tip Clearance—Casing Treatment on Performance and Stability of a Transonic Axial Compressor
,”
ASME J. Turbomach.
,
126
(
4
), pp.
527
535
.
12.
Weichert
,
S.
,
Day
,
I.
, and
Freeman
,
C.
,
2011
, “
Self-Regulating Casing Treatment for Axial Compressor Stability Enhancement
,”
ASME
Paper No. GT2011-46042.
13.
Wu
,
H.
,
Tan
,
D.
,
Miorini
,
R. L.
, and
Katz
,
J.
,
2011
, “
Three-Dimensional Flow Structures and Associated Turbulence in the Tip Region of a Waterjet Pump Rotor Blade
,”
Exp. Fluids
,
51
(
6
), pp.
1721
1737
.
14.
Miorini
,
R. L.
,
Wu
,
H.
, and
Katz
,
J.
,
2012
, “
The Internal Structure of the Tip Leakage Vortex Within the Rotor of an Axial Waterjet Pump
,”
ASME J. Turbomach.
,
134
(
3
), p.
31018
.
15.
Tan
,
D.
,
Li
,
Y.
,
Wilkes
,
I.
,
Miorini
,
R.
, and
Katz
,
J.
,
2015
, “
Visualization and Time Resolved PIV Measurements of the Flow in the Tip Region of a Subsonic Compressor Rotor
,”
ASME J. Turbomach.
,
137
(
4
), p.
41007
.
16.
Wu
,
H.
,
Miorini
,
R. L.
, and
Katz
,
J.
,
2011
, “
Measurements of the Tip Leakage Vortex Structures and Turbulence in the Meridional Plane of an Axial Water-Jet Pump
,”
Exp. Fluids
,
50
(
4
), pp.
989
1003
.
17.
Wu
,
H.
,
Miorini
,
R. L.
,
Tan
,
D.
, and
Katz
,
J.
,
2012
, “
Turbulence Within the Tip-Leakage Vortex of an Axial Waterjet Pump
,”
AIAA J.
,
50
(
11
), pp.
2574
2587
.
18.
Tan
,
D.
,
Li
,
Y.
,
Chen
,
H.
,
Wilkes
,
I.
, and
Katz
,
J.
,
2015
, “
The Three Dimensional Flow Structure and Turbulence in the Tip Region of an Axial Flow Compressor
,”
ASME
Paper No. GT2015-43385.
19.
Li
,
Y.
,
Chen
,
H.
, and
Katz
,
J.
,
2017
, “
Measurements and Characterization of Turbulence in the Tip Region of an Axial Compressor Rotor
,”
ASME J. Turbomach.
,
139
(
12
), p.
121003
.
20.
Chen
,
H.
,
Li
,
Y.
,
Tan
,
D.
, and
Katz
,
J.
,
2017
, “
Visualizations of Flow Structures in the Rotor Passage of an Axial Compressor at the Onset of Stall
,”
ASME J. Turbomach.
,
139
(
4
), p.
41008
.
21.
Li
,
Y.
,
Chen
,
H.
,
Tan
,
D.
, and
Katz
,
J.
,
2016
, “
Effects of Tip Clearance and Operating Conditions on the Flow Structure and Reynolds Stresses Within an Axial Compressor Rotor Passage
,”
ASME
Paper No. GT2016-57050.
22.
Chen
,
H.
,
Li
,
Y.
,
Koley
,
S. S.
,
Doeller
,
N.
, and
Katz
,
J.
,
2017
, “
An Experimental Study of Stall Suppression and Associated Changes to the Flow Structures in the Tip Region of an Axial Low Speed Fan Rotor by Axial Casing Grooves
,”
ASME J. Turbomach.
,
139
(
12
), p.
121010
.
23.
Hah
,
C.
,
Hathaway
,
M.
, and
Katz
,
J.
,
2014
, “
Investigation of Unsteady Flow Field in a Low-Speed One and a Half Stage Axial Compressor—Part 2: Effects of Tip Gap Size on the Tip Clearance Flow Structure At Near Stall Operation
,”
ASME
Paper No. GT2014-27094.
24.
Bai
,
K.
, and
Katz
,
J.
,
2014
, “
On the Refractive Index of Sodium Iodide Solutions for Index Matching in PIV
,”
Exp. Fluids
,
55
(
4
), pp.
1
6
.
25.
Wu
,
H.
,
Miorini
,
R. L.
, and
Katz
,
J.
,
2009
, “
The Inner structure and Turbulent Evolution of the Tip Leakage Vortex in An Axial Pump—Part I: Instantaneous Results
,”
ASME
Paper No. FEDSM2009-78534.
26.
Wieneke
,
B.
,
2005
, “
Stereo-PIV Using Self-Calibration on Particle Images
,”
Exp. Fluids
,
39
(
2
), pp.
267
280
.
27.
Roth
,
G. I.
, and
Katz
,
J.
,
2001
, “
Five Techniques for Increasing the Speed and Accuracy of PIV Interrogation
,”
Meas. Sci. Technol.
,
12
(
3
), pp.
238
245
.
28.
Westerweel
,
J.
, and
Scarano
,
F.
,
2005
, “
Universal Outlier Detection for PIV Data
,”
Exp. Fluids
,
39
(
6
), pp.
1096
1100
.
29.
Inoue
,
M.
, and
Kuroumaru
,
M.
,
1989
, “
Structure of Tip Clearance Flow in an Isolated Axial Compressor Rotor
,”
ASME J. Turbomach.
,
111
(
3
), p.
250
.
You do not currently have access to this content.