This paper presents an experimental study of the behavior of leakage flow across shrouded turbine blades. Stereoscopic particle image velocimetry and fast response aerodynamic probe measurements have been conducted in a low-speed two-stage axial turbine with a partial shroud. The dominant flow feature within the exit cavity is the radially outward motion of the main flow into the shroud cavity. The radial migration of the main flow is induced by flow separation at the trailing edge of the shroud due to a sudden area expansion. The radially outward motion is the strongest at midpitch as a result of interactions between vortices formed within the cavity. The main flow entering the exit cavity divides into two streams. One stream moves upstream toward the adjacent seal knife and reenters the main flow stream. The other stream moves downstream due to the interaction with the thin seal leakage flow layer. Closer to the casing wall, the flow interacts with the underturned seal leakage flow and gains swirl. Eventually, axial vorticity is generated due to these complex flow interactions. This vorticity is generated by a vortex tilting mechanism and gives rise to additional secondary flow. Because of these fluid motions combined with a contoured casing wall, three layers (the seal leakage layer, cavity flow layer, and main flow) are formed downstream of the shroud cavity. This result is different from the two-layer structure, which is found downstream of conventional shroud cavities. The seal leakage jet formed through the seal clearance still exists at 25.6% axial chord downstream of the second rotor. This delay of complete dissipation of the seal leakage jet and its mixing with the cavity flow layer is due to the contoured casing wall. Time-averaged flow downstream of the shroud cavity shows the upstream stator’s influence on the cavity flow. The time-averaged main flow can be viewed as a wake flow induced by the upstream stator whose separation at the shroud trailing edge induces pitchwise non-uniformity of the cavity flow.
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e-mail: yongil.yun@samsung.com
e-mail: luca.porreca@ch.manturbo.com
e-mail: kalfas@lsm.iet.mavt.ethz.ch
e-mail: sjsong@snu.ac.kr
e-mail: abhari@lsm.iet.mavt.ethz.ch
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January 2008
Research Papers
Investigation of Three-Dimensional Unsteady Flows in a Two-Stage Shrouded Axial Turbine Using Stereoscopic PIV—Kinematics of Shroud Cavity Flow
Yong Il Yun,
Yong Il Yun
School of Mechanical and Aerospace Engineering,
e-mail: yongil.yun@samsung.com
Seoul National University
, Seoul 151-742, Korea
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Luca Porreca,
Luca Porreca
Turbomachinery Laboratory,
e-mail: luca.porreca@ch.manturbo.com
Swiss Federal Institute of Technology Zurich
, Zurich CH-8092, Switzerland
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Anestis I. Kalfas,
Anestis I. Kalfas
Turbomachinery Laboratory,
e-mail: kalfas@lsm.iet.mavt.ethz.ch
Swiss Federal Institute of Technology Zurich
, Zurich CH-8092, Switzerland
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Seung Jin Song,
Seung Jin Song
School of Mechanical and Aerospace Engineering,
e-mail: sjsong@snu.ac.kr
Seoul National University
, Seoul 151-742, Korea
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Reza S. Abhari
Reza S. Abhari
Turbomachinery Laboratory,
e-mail: abhari@lsm.iet.mavt.ethz.ch
Swiss Federal Institute of Technology Zurich
, Zurich CH-8092, Switzerland
Search for other works by this author on:
Yong Il Yun
School of Mechanical and Aerospace Engineering,
Seoul National University
, Seoul 151-742, Koreae-mail: yongil.yun@samsung.com
Luca Porreca
Turbomachinery Laboratory,
Swiss Federal Institute of Technology Zurich
, Zurich CH-8092, Switzerlande-mail: luca.porreca@ch.manturbo.com
Anestis I. Kalfas
Turbomachinery Laboratory,
Swiss Federal Institute of Technology Zurich
, Zurich CH-8092, Switzerlande-mail: kalfas@lsm.iet.mavt.ethz.ch
Seung Jin Song
School of Mechanical and Aerospace Engineering,
Seoul National University
, Seoul 151-742, Koreae-mail: sjsong@snu.ac.kr
Reza S. Abhari
Turbomachinery Laboratory,
Swiss Federal Institute of Technology Zurich
, Zurich CH-8092, Switzerlande-mail: abhari@lsm.iet.mavt.ethz.ch
J. Turbomach. Jan 2008, 130(1): 011021 (9 pages)
Published Online: January 28, 2008
Article history
Received:
June 3, 2006
Revised:
October 9, 2006
Published:
January 28, 2008
Citation
Il Yun, Y., Porreca, L., Kalfas, A. I., Jin Song, S., and Abhari, R. S. (January 28, 2008). "Investigation of Three-Dimensional Unsteady Flows in a Two-Stage Shrouded Axial Turbine Using Stereoscopic PIV—Kinematics of Shroud Cavity Flow." ASME. J. Turbomach. January 2008; 130(1): 011021. https://doi.org/10.1115/1.2720873
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