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Research Papers

Visualization and Time-Resolved Particle Image Velocimetry Measurements of the Flow in the Tip Region of a Subsonic Compressor Rotor

[+] Author and Article Information
David Tan

Department of Mechanical Engineering,
Johns Hopkins University,
223 Latrobe Hall,
3400 N. Charles Street,
Baltimore, MD 21218
e-mail: dtan4@jhu.edu

Yuanchao Li

Department of Mechanical Engineering,
Johns Hopkins University,
223 Latrobe Hall,
3400 N. Charles Street,
Baltimore, MD 21218
e-mail: yli131@jhu.edu

Ian Wilkes

Department of Mechanical Engineering,
Johns Hopkins University,
223 Latrobe Hall,
3400 N. Charles Street,
Baltimore, MD 21218
e-mail: iwilkes1@jhu.edu

Rinaldo L. Miorini

Department of Mechanical Engineering,
Johns Hopkins University,
223 Latrobe Hall,
3400 N. Charles Street,
Baltimore, MD 21218
e-mail: Rinaldo.Miorini@ge.com

Joseph Katz

Department of Mechanical Engineering,
Johns Hopkins University,
223 Latrobe Hall,
3400 N. Charles Street,
Baltimore, MD 21218
e-mail: katz@jhu.edu

1Corresponding author.

Contributed by the International Gas Turbine Institute (IGTI) of ASME for publication in the JOURNAL OF TURBOMACHINERY. Manuscript received August 11, 2014; final manuscript received August 15, 2014; published online October 28, 2014. Editor: Ronald Bunker.

J. Turbomach 137(4), 041007 (Oct 28, 2014) (11 pages) Paper No: TURBO-14-1205; doi: 10.1115/1.4028433 History: Received August 11, 2014; Revised August 15, 2014

A new optically index matched facility has been constructed to investigate tip flows in compressor-like settings. The blades of the one and a half stage compressor have the same geometry, but lower aspect ratio as the inlet guide vanes (IGVs) and the first stage of the low-speed axial compressor (LSAC) facility at NASA Glenn. With transparent blades and casings, the new setup enables unobstructed velocity measurements at any point within the tip region and is designed to facilitate direct measurements of effects of casing treatments on the flow structure. We start with a smooth endwall casing. High speed movies of cavitation and time-resolved PIV measurements have been used to characterize the location, trajectory, and behavior of the tip leakage vortex (TLV) for two flow rates, the lower one representing prestall conditions. Results of both methods show consistent trends. As the flow rate is reduced, TLV rollup occurs further upstream, and its initial orientation becomes more circumferential. At prestall conditions, the TLV is initially aligned slightly upstream of the rotor passage, and subsequently forced downstream. Within the passage, the TLV breaks up into a large number of vortex fragments, which occupy a broad area. Consequently, the cavitation in the TLV core disappears. With decreasing flow rate, this phenomenon becomes more abrupt, occurs further upstream, and the fragments occupy a larger area.

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References

Figures

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Fig. 1

Top view of relevant component of the optical refractive index matched facility

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Fig. 2

Meridional section of the refractive index matched low-speed compressor (a) and selected cross section (b) indicating the location of static pressure taps

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Fig. 3

(a) 3D drawing of the 1½ stage machine including PIV laser sheet dissecting the TLV and (b) schematics of the rotor blade including definition of the blade fraction (s/c). SS: suction side. PS: pressure side.

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Fig. 4

Static-to-static pressure coefficient versus flowrate coefficient at 480 RPM

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Fig. 5

(a) Flow visualization experiment setup and (b) high speed, planar PIV setup

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Fig. 6

Visualization of the TLV trajectory using cavitation at (a) maximum flowrate and (b) rotating stall inception condition; image (c) highlights the different trajectories with respect to the tangential direction

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Fig. 7

High speed images of the cavitating TLV showing fluctuation of the TLV trajectory angle at φ = 0.35 and φ = 0.33, i.e., near stall condition

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Fig. 8

Position and extents of the PIV domain in the rotor, origin of the axial coordinate corresponds to the position of the rotor blade tip LE as it passes through the meridional plane

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Fig. 9

Selected snapshots of the instantaneous flow in the meridional plane including contours of the circumferential vorticity at (a) φ = 0.33, and chord fractions (s/c): 0.546 and (b) 0.819, and at (c) φ = 0.25, and chord fractions (s/c): 0.546 and (d) 0.819. High speed images of the cavitating TLV dissected by the same meridional plane are also shown for comparison.

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Fig. 10

Cross sections of the same instantaneous TLV captured as it passes through the meridional plane at φ = 0.33. Contours of the circumferential vorticity are shown together with position of the rotor blade section at chord fractions (s/c): (a) − 0.109, (b) 0.00, (c) 0.109, (d) 0.218, (e) 0.328, (f) 0.437, (g) 0.546, (h) 0.655, (i) 0.764, (l) 0.873, (m) 0.983, and (n) 1.092.

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Fig. 11

Cross sections of the same instantaneous TLV captured as it passes through the meridional plane at φ = 0.25, i.e., near stall. Contours of the circumferential vorticity are shown together with position of the rotor blade section at chord fractions (s/c): (a)−0.109, (b) 0.00, (c) 0.109, (d) 0.218, (e) 0.328, (f) 0.437, (g) 0.546, (h) 0.655, (i) 0.764, (l) 0.873, (m) 0.983, and (n) 1.092.

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Fig. 12

Cross sections of two different TLVs captured at φ = 0.33 (a1–c1) and at near-stall condition, i.e., φ = 0.25 (a2–c2) indicating the different propagation rate of the vortex. TLV sections are captured at chord fractions (s/c): 0.164 (a1, a2), 0.382 (b1, b2), and 0.600 (c1, c2).

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