0
Research Papers

Visualizations of Flow Structures in the Rotor Passage of an Axial Compressor at the Onset of Stall

[+] Author and Article Information
Huang Chen

Department of Mechanical Engineering,
Johns Hopkins University,
223 Latrobe Hall,
3400 N. Charles Street,
Baltimore, MD 21218
e-mail: hchen98@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

David Tan

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

Joseph Katz

Department of Mechanical Engineering,
Johns Hopkins University,
122 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 September 20, 2016; final manuscript received September 28, 2016; published online January 10, 2017. Editor: Kenneth Hall.

J. Turbomach 139(4), 041008 (Jan 10, 2017) (14 pages) Paper No: TURBO-16-1249; doi: 10.1115/1.4035076 History: Received September 20, 2016; Revised September 28, 2016

Experiments preformed in the JHU refractive index matched facility examine flow phenomena developing in the rotor passage of an axial compressor at the onset of stall. High-speed imaging of cavitation performed at low pressures qualitatively visualizes vortical structures. Stereoscopic particle image velocimetry (SPIV) measurements provide detailed snapshots and ensemble statistics of the flow in a series of meridional planes. At prestall condition, the tip leakage vortex (TLV) breaks up into widely distributed intermittent vortical structures shortly after rollup. The most prominent instability involves periodic formation of large-scale backflow vortices (BFVs) that extend diagonally upstream, from the suction side (SS) of one blade at midchord to the pressure side (PS) near the leading edge of the next blade. The 3D vorticity distributions obtained from data recorded in closely spaced planes show that the BFVs originate form at the transition between the high circumferential velocity region below the TLV center and the main passage flow radially inward from it. When the BFVs penetrate to the next passage across the tip gap or by circumventing the leading edge, they trigger a similar phenomenon there, sustaining the process. Further reduction in flow rate into the stall range increases the number and size of the backflow vortices, and they regularly propagate upstream of the leading edge of the next blade, where they increase the incidence angle in the tip corner. As this process proliferates circumferentially, the BFVs rotate with the blades, indicating that there is very little through flow across the tip region.

FIGURES IN THIS ARTICLE
<>
Copyright © 2017 by ASME
Your Session has timed out. Please sign back in to continue.

References

Figures

Grahic Jump Location
Fig. 1

Configuration of the one and a half stages compressor

Grahic Jump Location
Fig. 2

(a) Static-to-static and (b) total-to-static performance curves at 480 RPM for an h/c = 2.3% tip gap

Grahic Jump Location
Fig. 3

Setups for (a) SPIV in meridional planes and (b) cavitation flow visualization

Grahic Jump Location
Fig. 4

Rotor blade tip profile with horizontal lines highlighting the SPIV measurement sample areas

Grahic Jump Location
Fig. 5

Ensemble-averaged contours of <ωθ> (top row) and <uθ> (bottom row) at: (a) and (b) s/c = 0.16, (c) and (d) s/c = 0.33, and (e) and (f) s/c = 0.76. Lines in (b), (d), and (f) are contours of <ωθ>, with dashed lines indicating negative values. Vectors in (a) are shown in full resolution for part of the sample area. In (c) and (e), vectors are diluted by 2:1 axially and 2:1 radially for clarity. Note the differences in vorticity scale. A reference vector showing the tip speed is provided on top. Horizontal axis is the streamwise direction while vertical axis is the radial direction. Other plots of SPIV results follow the same convention.

Grahic Jump Location
Fig. 6

A sample instantaneous realization of (a) ωθ and (b) uθ at s/c = 0.33, representing conditions when the blade tip is not stalled. Vectors in (b) are diluted by 2:1 axially and 2:1 radially. Note the differences in scales.

Grahic Jump Location
Fig. 7

Contours of the TKE at (a) s/c = 0.16, (b) s/c = 0.33, and (c) s/c = 0.76 at φ = 0.25. (d) TKE at φ = 0.35 and s/c = 0.33, the same location as (b), aimed at highlighting differences between them. Note the differences in scale. Lines are contour of <ωθ>, with dashed lines indicating negative values.

Grahic Jump Location
Fig. 8

A time sequence of cavitation images showing the propagation of vortical structures at prestall conditions. Arrows of same styles follow the evolution of the same backflow vortex. White lines indicate the blade tip profile.

Grahic Jump Location
Fig. 9

Sample cavitation images showing (a) TLV without the influence of the backflow vortex and (b) the backflow vortex propagating across the tip gap

Grahic Jump Location
Fig. 10

Ensemble-averaged three-dimensional velocity and vorticity distributions in the meridional plane at s/c = 0.44 and φ = 0.25. (a)–(c) Plots of <uθ>, <uz>, and <ur>. (d) Velocity diagram for points A and B, explaining the orientation of the backflow vortices. (e)–(g) Distributions of <ωθ>, <ωz>, and <ωr>. (h) Vorticity diagram for point C, explaining the direction of the backflow vortices. (i) Perspective view of circumferential velocity distribution with three-dimensional velocity vectors. The elevation of the protruding surface is proportional to <uθ>. Vectors are diluted by 2:1 axially and radially. (j) Sketch of vortical layers originating from the tip gap, and surrounding the TLV. Background is the <uθ> contour. Lines in (a), (f), and (g) are contours of <ωθ>, with dashed lines indicating negative values.

Grahic Jump Location
Fig. 11

Samples of instantaneous realizations of <ωθ> (top row) and <uθ> (bottom row) at (a) and (b) s/c = 0.16, (c) and (d) s/c = 0.33 and (e) and (f) s/c = 0.76, when the backflow vortices interact with the adjacent blade. Vectors are diluted by 2:1 axially and 2:1 radially. Lines in (b), (d), and (f) are contours of <ωθ>, with dashed lines indicating negative values.

Grahic Jump Location
Fig. 12

(a) <uθ> and (b) an instantaneous sample uθ at the leading edge at φ = 0.25. Vectors are diluted by 2:1 axially and 2:1 radially.

Grahic Jump Location
Fig. 13

Relative incidence angles (angles relative to the meridional plane) at s/c = −0.16. (a) A sketch showing the definition of incidence angle. (b) Ensemble-averaged result of 2500 realizations. (c) Conditionally averaged result of 100 extreme cases when backflow vortices reaching near the LE. (d) The change in incidence angle. Dot line indicates the location of the leading edge. The circle indicates the location used for conditional sampling.

Grahic Jump Location
Fig. 14

Sample unrelated snapshots of huge backflow vortices in the rotor passage at stall conditions

Tables

Errata

Discussions

Some tools below are only available to our subscribers or users with an online account.

Related Content

Customize your page view by dragging and repositioning the boxes below.

Related Journal Articles
Related eBook Content
Topic Collections

Sorry! You do not have access to this content. For assistance or to subscribe, please contact us:

  • TELEPHONE: 1-800-843-2763 (Toll-free in the USA)
  • EMAIL: asmedigitalcollection@asme.org
Sign In