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Research Papers

Particle Image Velocimetry Measurements in a Two-Pass 90 Degree Ribbed-Wall Parallelogram Channel

[+] Author and Article Information
Tong-Miin Liou

Department of Power Mechanical Engineering,
National Tsing Hua University,
No. 101, Section 2, Kuang-Fu Road,
Hsinchu 30013, Taiwan
e-mail: tmliou@pme.nthu.edu.tw

Shyy-Woei Chang

Thermal Fluids Laboratory,
National Kaohsiung Marine University,
No. 142, Haijhuan Road, Nanzih District,
Kaohsiung City 81143, Taiwan
e-mail: swchang@mail.nkmu.edu.tw

Shu-Po Chan

Department of Power Mechanical Engineering,
National Tsing Hua University,
No. 101, Section 2, Kuang-Fu Road,
Hsinchu 30013, Taiwan
e-mail: tedchan0611@gmail.com

Yu-Shuai Liu

Department of Power Mechanical Engineering,
National Tsing Hua University,
No. 101, Section 2, Kuang-Fu Road,
Hsinchu 30013, Taiwan
e-mail: lyushuai@gmail.com

1Corresponding author.

Contributed by the International Gas Turbine Institute (IGTI) of ASME for publication in the JOURNAL OF TURBOMACHINERY. Manuscript received September 15, 2014; final manuscript received September 18, 2014; published online November 26, 2014. Editor: Ronald Bunker.

J. Turbomach 137(4), 041012 (Apr 01, 2015) (10 pages) Paper No: TURBO-14-1243; doi: 10.1115/1.4028739 History: Received September 15, 2014; Revised September 18, 2014; Online November 26, 2014

A parallelogram channel has drawn very little or no attention in the open literature although it appears as a cross-sectional configuration of some gas turbine rotor blades. Particle image velocimetry (PIV) is presented of local flow structure in a two-pass 90 deg ribbed-wall parallelogram channel with a 180 deg sharp turn. The channel has a cross-sectional equal length, 45.5 mm, of adjacent sides and two pairs of opposite angles are 45 deg and 135 deg. The rib height to channel height ratio is 0.1. All the measurements were performed at a fixed Reynolds number, characterized by channel hydraulic diameter of 32.17 mm and cross-sectional bulk mean velocity, of 10,000 and a null rotating number. Results are discussed in terms of the distributions of streamwise and secondary-flow mean velocity vector, turbulent intensity, Reynolds stress, and turbulent kinetic energy of the cooling air. It is found that the flow is not periodically fully developed in pitchwise direction through the inline 90 deg ribbed straight inlet and outlet leg. Pitchwise variation of reattachment length is revealed, and comparison with reported values in square channels is made. Whether the 180 deg sharp turn induced separation bubble exists in the ribbed parallelogram channel is also documented. Moreover, the measured secondary flow results inside the turn are successively used to explain previous heat transfer trends.

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Figures

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Fig. 1

Sketch of configuration, coordinate system, and dimensions of parallelogram test section

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Fig. 2

The test facility of internal coolant passage with parallelogram cross section

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Fig. 3

Measured transverse profiles of U/Ub and u'/Ub along Z *= −0.5 centerline at inlet reference station for ribbed-wall and smooth-wall case

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Fig. 4

Mean flow patterns in terms of velocity vectors, contours of U/Ub, V/Ub, K/Ub2, and -uv¯/Ub2, and comparison of U/Ub profiles in some selected pitches on Z *= −0.5 plane of first pass: (a) mean flow patterns in terms of velocity vectors in four selected pitches of first pass, (b) portion enlarged view of (a), (c) contours of U/Ub, V/Ub, K/Ub2, and -uv¯/Ub2 in third pitch, and (d) comparison of streamwise mean velocity profiles between the fourth and sixth pitch at three selected x/H

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Fig. 5

Streamwise evolution of midpitch U/Ub profile in the horizontal cut plane of Y *= 0

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Fig. 6

Mean flow patterns in terms of velocity vectors in four selected pitches on Z*= 0.5 plane of second pass as well as variation of the reattachment length with pitch index in the first and second pass [28,3537]: (a) mean flow patterns in terms of velocity vectors in four selected pitches of second pass, (b) portion enlarged view of (a), and (c) reattachment length versus pitch index [28,36,37]

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Fig. 7

Flow pattern inside and around bend region: (a) flow pattern inside and around bend region on Y*= 0 plane, (b) enlarged view of dashed box in (a) on Y*= 0 plane, (c) flow visualization of dashed box in (a) on Y*= 0 plane, and (d) enlarged view of dashed box in (a) on Y*= 0.44 plane (2 mm away from ribbed top wall)

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Fig. 8

Evolution of PIV measured secondary flow pattern (facing downstream) in the turn region: (a) an overall view for the five cross sections selected (⊙: flow out of first pass and ⊗: flow into the second pass), (b) θ = 0 deg at turn, (c) θ = 45 deg at turn, (d) θ = 90 deg at turn, (e) θ = 135 deg at turn, and (f) θ = 180 deg at turn

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Fig. 9

Correlation between top-wall Nu/Nu0 distribution (along Y *= 0.5 in Fig. 7(d)) and near-wall mean and turbulent parameters (2 mm away from the top wall): (a) at θ = 90 deg of turn and (b) at θ = 180 deg of turn

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