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Research Papers

Measurements and Characterization of Turbulence in the Tip Region of an Axial Compressor Rotor

[+] Author and Article Information
Yuanchao Li

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

Huang Chen

Department of Mechanical Engineering,
Johns Hopkins University,
223 Latrobe Hall, 3400 N. Charles Street,
Baltimore, MD 21218
e-mail: hchen98@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 August 3, 2017; final manuscript received August 18, 2017; published online September 26, 2017. Editor: Kenneth Hall.

J. Turbomach 139(12), 121003 (Sep 26, 2017) (10 pages) Paper No: TURBO-17-1103; doi: 10.1115/1.4037773 History: Received August 03, 2017; Revised August 18, 2017

Modeling of turbulent flows in axial turbomachines is challenging due to the high spatial and temporal variability in the distribution of the strain rate components, especially in the tip region of rotor blades. High-resolution stereo-particle image velocimetry (SPIV) measurements performed in a refractive index-matched facility in a series of closely spaced planes provide a comprehensive database for determining all the terms in the Reynolds stress and strain rate tensors. Results are also used for calculating the turbulent kinetic energy (TKE) production rate and transport terms by mean flow and turbulence. They elucidate some but not all of the observed phenomena, such as the high anisotropy, high turbulence levels in the vicinity of the tip leakage vortex (TLV) center, and in the shear layer connecting it to the blade suction side (SS) tip corner. The applicability of popular Reynolds stress models based on eddy viscosity is also evaluated by calculating it from the ratio between stress and strain rate components. Results vary substantially, depending on which components are involved, ranging from very large positive to negative values. In some areas, e.g., in the tip gap and around the TLV, the local stresses and strain rates do not appear to be correlated at all. In terms of effect on the mean flow, for most of the tip region, the mean advection terms are much higher than the Reynolds stress spatial gradients, i.e., the flow dynamics is dominated by pressure-driven transport. However, they are of similar magnitude in the shear layer, where modeling would be particularly challenging.

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References

Figures

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Fig. 1

(a) Three blade rows of the compressor, (b) experimental setup for SPIV measurements, and (c) the three-dimensional (3D) domain at 0.432 < s/c < 0.442 containing 11 closely spaced meridional sample planes

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Fig. 2

Performance curve for the compressor with tip clearance of h/c = 2.3% and a smooth endwall. The operating condition for the present analysis is highlighted by a circle.

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Fig. 3

(a) A perspective view illustrates the three-dimensional ensemble-averaged velocity distributions using vectors for the in-plane velocity (Uz, Ur), as well as elevation and contours for the out-of-plane velocity (Uθ) in a rotating reference frame. The vectors are diluted by 3:1 in the z-direction for clarity. A white dot marks the TLV center. (b)–(d) Distributions of the ensemble-averaged radial, circumferential and axial vorticity, respectively. The dashed lines follow the locations of zero values.

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Fig. 4

Distributions of (a) TKE and three Reynolds normal stresses, (b) 〈u′z2〉, (c) 〈u′r2〉, and (d) 〈u′θ2 〉 for φ = 0.35 and h/c = 2.3%. The white contour lines show the distribution of 〈ωθ〉.

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Fig. 5

Distributions of TKE for (a) φ = 0.35, h/c = 0.49% and (b) φ = 0.25, h/c = 2.3%. The white contour lines show the distribution of 〈ωθ〉.

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Fig. 6

Dominant terms in the production rate of Reynolds normal stresses: (a) −2〈u′z2〉∂zUz (ΩUT2)−1, (b) −2〈u′zu′r〉∂rUz (ΩUT2)−1, (c) −2〈u′ru′z〉∂zUr (ΩUT2)−1, (d) −2〈u′r2〉∂rUr (ΩUT2)−1, (e) −2〈u′ru′θ〉∂rUθ (ΩUT2)−1, and (f) −2r1〈u′θ2〉∂θUθ (ΩUT2)−1

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Fig. 7

Terms in the transport equation for TKE: (a) production rate, (b) advection by mean flow, (c) turbulent transport, (d) dissipation rate (underestimated), (e) viscous diffusion, and (f) P + A + T + M − ε*

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Fig. 8

Distribution of production-based eddy viscosity. Dashed contour lines follow the locations of zero values.

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Fig. 9

Distributions of: (top row) mean shear strain rate components; (middle row) Reynolds shear stresses, and (bottom row) corresponding eddy viscosity: (a) Srz, (b) S, (c) S, (d) −〈u′ru′z〉, (e) −〈u′zu′θ〉, (f) −〈u′ru′θ〉, (g) νT,rz, (h) νT,, and (i) νT,. Dashed lines follow the locations of zero values.

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Fig. 10

Distribution of the ratio indicator ρRS

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Fig. 11

Distributions of (a) mean advection term for axial velocity, (b) the corresponding divergence of measured deviatoric Reynolds stresses, and (c) the magnitude ratio between them

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